Microcrystalline wax is a solid obtained by extracting the oil from petrolatum. It is a complex mixture composed mainly of C31–C70 isoparaffins. It has a microcrystalline structure, high adhesive power, good extensibility, is not susceptible to low temperatures and has a high melting point (60–85°C). When mixed with other waxes, it suppresses crystal formation making it useful in lipsticks and creams.

Source: Cosmetic Formulation Principles and Practice - Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters

The main components are long-chain wax esters with chain lengths of around C60. Although it has
similar chemistry to sunflower wax, its applications are quite different. Refined rice bran wax has a very
hydrophobic character. It forms soft oil gels and is therefore highly preferred for emulsions like mascaras
and skin care products.

Source: Cosmetic Formulation Principles and Practice - Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters

The wax obtained from sunflower oil forms hard and very homogeneous thermally stable oil gels and is therefore excellent for light-coloured, practically odorless and tasteless lip balms, lipsticks and other oil gels. Chemically it has a long chain (about C60) wax ester mainly from monovalent alcohols and acids. Sunflower wax has a melting point of about 80°C and a narrow melting curve with no molten contents below 55°C. Consequently the oil gels are very heat resistant.

Source: Cosmetic Formulation Principles and Practice - Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters

What Is Candelilla Wax?

Candelilla Wax is obtained from the above-ground parts of wild Euphorbia cerifera. The plant is dried and boiled in water, after which the wax is separated by decanting. Crude candelilla wax is dark brown and is refined to produce a pale yellow wax.

Candelilla Wax is remarkably hard but has relatively low crystallinity. At higher temperatures, it also exhibits a certain degree of tackiness.

Key Properties of Candelilla Wax

Hardness and Structure
Candelilla Wax provides hardness and structure to cosmetic formulations and is particularly useful in solid products.

Oil-Binding Capacity
Its resin and sitosterol content, together with esters, gives candelilla wax an excellent capacity for binding ester oils.

Melting Point
Its melting point is approximately 72°C, placing it between beeswax and carnauba wax. This makes it useful for controlling the consistency and melting behaviour of cosmetic products.

Gloss and Contraction
Candelilla Wax provides a high surface gloss and has satisfactory contraction properties, which are particularly useful during lipstick manufacturing and demoulding.

Cosmetic Applications

Candelilla Wax is especially suitable for:

• Lipsticks
• Lip balms
• Decorative cosmetics
• Solid oil-based formulations

In lipsticks, it contributes hardness, oil binding and surface gloss while its contraction properties support easier demoulding during manufacturing.

Ingredient Information

INCI: Euphorbia Cerifera Wax
CAS: 8006-44-8
EINECS/EC: 232-347-0

References

Cosmetic Formulation Principles and Practice – Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters.

What Is Carnauba Wax?

Carnauba Wax is produced by the Brazilian palm Copernicia cerifera, which deposits the wax on the cuticle of its fronds. The leaves are harvested, dried in the sun and threshed to obtain the wax.

Carnauba Wax has a narrow melting range with a melting point of approximately 84°C. Its high crystallinity and strong contraction make it a very hard and brittle wax.

Key Properties of Carnauba Wax

High Melting Point
Its high melting point makes Carnauba Wax useful for increasing the melting point and structural stability of oil-based formulations.

Hardness and Structure
The wax provides firmness and structure, making it particularly useful in solid and stick-type cosmetic products.

Emulsification and Oil-Binding Properties
Carnauba Wax has favourable emulsification properties and a strong capacity for binding ester oils and mineral oils.

Gloss and Lustre
It can provide a glossy, lustrous surface, which is particularly desirable in decorative cosmetics and lip products.

Cosmetic Applications

Carnauba Wax is commonly used in:

• Lipsticks
• Lip balms
• Mascaras
• Oil gels
• Decorative cosmetics

It is particularly valuable in lipsticks and lip balms because it raises the melting point of oil gels while providing the desired hardness and structure. Its ability to create glossy surfaces also makes it highly suitable for mascaras and other decorative products.

Ingredient Information

INCI: Copernicia Cerifera (Carnauba) Wax
CAS: 8015-86-9
EINECS/EC: 232-399-4

References

Cosmetic Formulation Principles and Practice – Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters.

What Is Cera Alba?

Beeswax is a secretion produced by the abdominal glands of honeybees. Freshly secreted beeswax is white and colourless, but it develops its characteristic colour as bees collect and store pollen and honey.

For cosmetic purposes, yellow beeswax is referred to as Cera Flava, while white beeswax is known as Cera Alba. Beeswax has a relatively low melting point of approximately 61–65°C and is moderately hard, while becoming somewhat sticky, plastic and kneadable at body temperature.

Key Properties of Beeswax

Excellent Oil-Binding Properties
Beeswax is one of the most effective oil-binding waxes used in cosmetics. This makes it particularly useful for creating rich, creamy textures.

Texturising and Film-Forming
It contributes structure, adhesion and a pleasant film on the skin, making it especially valuable in lip and skin-care products.

Emulsion Stabilisation
Its oil-gelling properties can help stabilise water-in-oil emulsions and provide the desired consistency in skin and hair formulations.

Cosmetic Applications

Beeswax is commonly used in:

• Lipsticks and lip balms
• Water-in-oil emulsions
• Skin and hair care products
• Mascara
• Make-up products

In decorative cosmetics, beeswax can enhance texture and add volume, while in lip products it helps create creamy textures, good adhesion and a pleasant protective film.

Ingredient Information

INCI: Cera Alba
CAS: 8012-89-3
EINECS/EC: 232-383-7

References

Cosmetic Formulation Principles and Practice – Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters.

What Are Waxes?

Waxes are mixtures of hydrophobic organic substances of medium-chain length. They melt at temperatures ranging from approximately 40°C to 140°C without decomposition and re-solidify without significant chemical change. Their solubility and consistency are strongly dependent on temperature.

Types of Waxes

Waxes can be classified according to their origin into three main groups:

Animal Waxes
These are obtained from animal-derived sources and have traditionally been used in cosmetic and personal care formulations.

Vegetable Waxes
These are obtained from plants and are widely used as alternatives to animal-derived waxes in cosmetic formulations.

Mineral Waxes
These are derived from mineral sources and are commonly used where specific texture, consistency and stability properties are required.

Cosmetic Applications

Waxes are important formulation ingredients because their physical properties change with temperature. They can contribute to the consistency and structure of cosmetic products and are therefore commonly incorporated into formulations where a defined texture and solid or semi-solid consistency are required.

They can be found in various cosmetic products, including creams, balms, lip products, ointments and decorative cosmetics.

Why Are Waxes Important in Formulation?

The melting behaviour and temperature-dependent consistency of waxes make them useful for controlling the physical characteristics of a formulation. Selecting the appropriate type and concentration of wax allows formulators to influence the structure, texture and overall sensory properties of the finished product.

References

Cosmetic Formulation Principles and Practice – Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters.

What Is a Unique Selling Point?

A Unique Selling Point or Unique Selling Proposition is a marketing concept that describes the one thing that makes a product or service different from the competition. It identifies what makes the offering special and worth buying.

A USP can be based on a product feature, benefit, technology, formulation, service, quality, positioning or another characteristic that provides meaningful differentiation.

What Makes a Good USP?

A strong USP should be:

Clear and Concise
The message should be easy to understand and communicate the main point without unnecessary complexity.

Believable
The USP should be credible and supported by the actual characteristics or benefits of the product or service.

Persuasive
It should communicate a compelling reason for customers to choose the product or service.

Relevant to the Target Audience
The USP should address something that is meaningful and valuable to the intended customer.

Why Is a USP Important?

A well-defined USP helps a brand differentiate itself in a competitive market. It provides a clear foundation for marketing communication and helps customers understand why a particular product or service is different from available alternatives.

USP in Cosmetic Product Development

In cosmetics, a USP can be built around factors such as a distinctive formulation, specific ingredient concept, sensory experience, product performance, sustainability approach or a clearly defined consumer benefit. A strong USP can therefore connect product development with brand positioning and marketing strategy.

What Is a Formulation?

A formulation is a mixture of ingredients combined in a specific way to achieve a defined purpose. In cosmetics, a formulation is the combination of ingredients that makes up a cosmetic product.

The formulation plays a central role in determining the product’s performance, appearance, texture, stability and shelf life.

Active and Inactive Ingredients

Cosmetic formulation ingredients can broadly be divided into two categories: active and inactive ingredients.

Active Ingredients
Active ingredients provide the desired cosmetic effect of a product. Depending on the formulation, they may contribute to moisturising, exfoliating, protecting or other intended skincare benefits.

Inactive Ingredients
Inactive ingredients support the overall performance, appearance and stability of the formulation. Examples include thickeners, preservatives and fragrances.

The Purpose of Cosmetic Formulation

The goal of cosmetic formulation is to create products that are safe, effective and appealing while meeting consumer expectations. A successful formulation must also comply with applicable regulatory requirements and quality standards within the cosmetics industry.

Why Is Formulation Important?

Formulation determines how the different ingredients work together within the finished product. The correct selection and combination of ingredients is therefore essential for achieving the desired sensory properties, performance, stability and shelf life of a cosmetic product.

What Are Ceramides?

Ceramides are amides of sphingosine and ω-hydroxy fatty acids, with the hydroxyl group esterified with linoleic acid. They are colourless, wax-like substances that are practically insoluble in water and are usually supplied in powder form.

Ceramides can be isolated from natural sources, although most ceramides used today are produced synthetically. They belong to the group of sphingolipids and are naturally present in the skin.

Ceramides and the Skin Barrier

Ceramides are the main intercellular lipids of the stratum corneum. Together with other skin lipids, they contribute to the organisation of lipid lamellar phases within the skin barrier.

Because of their structural role in the stratum corneum, ceramides are important ingredients in cosmetic formulations focused on maintaining skin conditioning and supporting the skin barrier.

Cosmetic Applications

Ceramides are particularly suitable for formulations designed for:

• Skin barrier support
• Dry and sensitive skin
• Skin-conditioning products
• Moisturising creams and lotions
• Facial and body care formulations

Their compatibility with the skin's naturally occurring lipid structures makes them valuable ingredients in modern barrier-focused skincare formulations.

Ingredient Information

INCI: Ceramides
CAS: Not specified on the original A&T Formulation page
EINECS/EC: Not specified on the original A&T Formulation page

References

Modern Cosmetics - Dr. Damjan Janeš and Dr. Nina Kočevar Glavač

What Is Pomegranate Seed Oil?

Pomegranate Seed Oil is obtained from the seeds of Punica granatum, a shrub or small tree originating from Iran and now cultivated widely across the Mediterranean, Africa, Southeast Asia, Australia and America. The seeds contain approximately 20% oil.

The oil has an unusually distinctive fatty acid composition, with punicic acid as its main component. Punicic acid is a rare omega-5 fatty acid belonging to the group of conjugated linolenic acids. Pomegranate oil also contains vitamin E and naturally occurring compounds including 17α-estradiol and estrone.

Key Properties of Pomegranate Seed Oil

Rich in Punicic Acid
The high content of punicic acid gives pomegranate oil its distinctive chemical profile and makes it an interesting ingredient for cosmetic formulations.

Antioxidant Properties
Pomegranate oil has demonstrated antioxidative activity in laboratory research and is used in formulations designed to help protect skin from oxidative stress.

Skin-Conditioning and Soothing
The oil is particularly suitable for formulations targeting mature, dry and stressed skin, where emollient and conditioning properties are desired.

High Oxidative Instability
Pomegranate Seed Oil is highly susceptible to oxidation. For this reason, it is recommended to combine it with more oxidation-stable vegetable oils and/or antioxidants when formulating with the pure oil.

Cosmetic Applications

Pomegranate Seed Oil can be used in a variety of skincare formulations, particularly:

• Mature and stressed skin products
• Dry and sensitive-skin formulations
• After-sun and skin-comfort products
• Facial oils and serums
• Regenerating and conditioning creams

Research described for pomegranate oil has reported anti-inflammatory, antioxidative and photoprotective effects, as well as effects associated with skin regeneration and keratinocyte proliferation. These findings support its use as a cosmetic ingredient for skin-conditioning formulations.

Ingredient Information

INCI: Punica Granatum Seed Oil
CAS: 84961-57-9
EINECS/EC: 284-646-0

References

Modern Cosmetics - Dr. Damjan Janeš and Dr. Nina Kočevar Glavač

What Is Mango Butter?

Mango (Mangifera indica) is a tropical tree originating from regions including Bangladesh, Myanmar, India and Indonesia. It is now commercially cultivated in many tropical regions around the world.

The mango fruit contains one large seed, from which Mango Butter is obtained. The seeds contain approximately 9–13% butter.

Mango Butter has a distinctive triglyceride composition characterised by a balanced proportion of predominant stearic and oleic acids. It also contains phytosterols, which may account for up to 7% of the butter.

The melting point is approximately 35°C. Mango Butter is relatively stable against oxidation and has a yellow to light-brown colour with a characteristic sweet, oily odour.

Key Properties of Mango Butter

Emollient Properties

Mango Butter is primarily used as an emollient ingredient in cosmetic formulations. It helps provide a soft, smooth and conditioned skin feel.

Rich in Phytosterols

The relatively high phytosterol content is an important characteristic of Mango Butter. These naturally occurring compounds contribute to its interest in cosmetic formulations focused on skin conditioning and antioxidant properties.

Alternative to Shea Butter

Because of its fatty acid composition, Mango Butter is particularly similar to Shea Butter and is often considered a useful alternative. Mango Butter is slightly more solid and contains less unsaponifiable matter than Shea Butter.

Mango Butter in Cosmetic Formulations

Skincare Products

Mango Butter is used in skin care products where emollient and conditioning properties are desired, particularly in formulations for dry or stressed skin.

Haircare Products

It can be incorporated into skin and hair cleansing products as well as hair-conditioning formulations.

Lip Care Products

Its rich, semi-solid consistency makes Mango Butter suitable for lip care products where a smooth and conditioned feel is desired.

Decorative Cosmetics

Mango Butter can also be used in decorative cosmetic formulations, contributing emollience and a pleasant texture.

Massage Products

Its consistency and melting characteristics make Mango Butter particularly suitable for massage formulations.

Mango Butter and Skin Conditioning

The phytosterol content of Mango Butter may contribute to its antioxidant properties and its ability to support the skin's lipid barrier.

Research described in the original A&T content has also investigated Mango Butter in emulsions in relation to skin recovery. These findings support its interest as a cosmetic ingredient for skin-conditioning formulations.

Raw Material and Processing Considerations

Mango seeds can contain up to 50% water and therefore need to be dried rapidly after harvesting. High moisture levels can promote microbial growth, particularly during the humid conditions that can coincide with the mango harvesting season in producing regions.

Microbial activity can also lead to degradation of triglycerides and an increase in free fatty acids. For this reason, appropriate drying, processing and storage of the raw material are important for maintaining the quality of Mango Butter.

Ingredient Information

INCI: Mangifera Indica Seed Oil

References

Source: Modern Cosmetics – Dr. Damjan Janeš and Dr. Nina Kočevar Glavač.

What Is Sweet Almond Oil?

Sweet Almond (Prunus amygdalus dulcis) is a shrub or, more typically, a tree that can grow 4–12 metres in height. It originates from regions extending from India to Asia Minor and was introduced to the Mediterranean in antiquity before later spreading to North America.

Sweet and bitter almonds are different varieties of the plant. Sweet almond produces edible fruit with a sweetish taste, while bitter almond produces bitter fruit.

The almond seeds contain approximately 50% oil. Sweet Almond Oil is particularly rich in oleic acid, with a considerable amount of linoleic acid and smaller amounts of saturated palmitic and stearic acids.

The oil has a light-yellow colour and a weak, sweetish-nutty odour. It can be obtained by cold pressing of almond seeds.

Key Properties of Sweet Almond Oil

Rich in Oleic Acid

Sweet Almond Oil is one of the vegetable oils particularly rich in oleic acid. This contributes to its characteristic emollient properties and makes it a versatile ingredient for skincare formulations.

Contains Linoleic Acid

Linoleic acid is another significant component of Sweet Almond Oil, contributing to its distinctive fatty acid profile and cosmetic properties.

Emollient Properties

Sweet Almond Oil is used as an emollient in cosmetic formulations, helping to provide a smooth, soft and conditioned skin feel.

Oxidative Stability

One important formulation consideration is that Almond Oil is relatively susceptible to oxidation. Appropriate storage, antioxidant protection and formulation design can therefore be important when working with the oil.

Cosmetic Applications

Skincare Products

Sweet Almond Oil is widely used in creams, lotions, facial oils and other skincare formulations where emollient and skin-conditioning properties are desired.

Body Care Products

Its pleasant sensory profile makes it suitable for body oils, body creams and other products designed to leave the skin feeling soft and conditioned.

Massage and Oil-Based Formulations

The oil's spreadability and emollient character make it suitable for massage oils and other oil-based cosmetic formulations.

Formulation Considerations

Because Sweet Almond Oil is relatively oxidatively unstable, formulators should consider its storage conditions, exposure to light and oxygen, and the use of appropriate antioxidant protection where necessary.

Its fatty acid profile and sensory characteristics also make it useful for blending with other vegetable oils to achieve the desired texture and formulation performance.

Ingredient Information

CAS: 8007-69-0 / 90320-37-9
EINECS/EC: 291-063-5

References

Source: Modern Cosmetics – Dr. Damjan Janeš and Dr. Nina Kočevar Glavač.

What Is Açai Oil?

Açai (Euterpe oleracea) is a palm native to the Amazon rainforest. Its fruit has been traditionally used for centuries in food, medicine and cosmetics and has become an important Brazilian export product.

The fruit pericarp contains approximately 25–50% oil. Açai Oil is characterised by a high content of oleic acid, followed by palmitic and linoleic acids. It also contains palmitoleic acid, which is relatively uncommon among vegetable oils.

Açai Oil is rich in phenolic compounds, including ferulic, p-hydroxybenzoic, protocatechuic, syringic and vanillic acids, as well as procyanidin dimers and trimers. These compounds contribute to the oil's oxidative stability.

The oil has a dark-green colour, a characteristic sweetish odour and a slightly higher viscosity than many conventional vegetable oils.

Key Properties of Açai Oil

Antioxidant Properties

The phenolic compounds naturally present in Açai Oil contribute to its antioxidant properties. In vitro studies have demonstrated antioxidant activity, making the oil interesting for cosmetic formulations focused on protecting the skin from oxidative stress.

Emollient Properties

Açai Oil provides emollient properties and can help improve the skin's softness and smoothness. Its relatively high palmitic acid content also makes it an interesting alternative to some vegetable butters, while providing a lighter, less greasy skin feel.

Rich in Fatty Acids

The combination of oleic, palmitic, linoleic and palmitoleic acids gives Açai Oil a distinctive fatty acid profile and contributes to its cosmetic functionality.

Cosmetic Applications

Mature Skin Care

Açai Oil is commonly used in products formulated for mature skin, where its antioxidant and emollient properties can support a smoother, conditioned and healthy-looking appearance.

Moisturisers and Creams

Its emollient properties make Açai Oil suitable for creams, lotions and other moisturising formulations where a pleasant, conditioned skin feel is desired.

Anti-Ageing Formulations

The antioxidant properties of Açai Oil make it relevant to cosmetic products targeting the visible signs of skin ageing and environmental oxidative stress.

Hair and Body Care

Açai Oil can also be incorporated into conditioning formulations for skin and hair where its emollient properties and distinctive botanical positioning are desirable.

Formulation Considerations

Açai Oil has a strong dark-green colour, which should be considered carefully when determining its concentration in a finished cosmetic product. Higher levels may noticeably influence the colour of the formulation.

Its high oleic acid content should also be considered when developing products intended for frequent or long-term use, particularly when selecting the overall fatty acid profile of the formulation.

Ingredient Information

CAS: 861902-11-6; 879496-95-4; 906351-38-0
EINECS/EC: 617-812-1

References

Source: Modern Cosmetics – Dr. Damjan Janeš and Dr. Nina Kočevar Glavač.

What Is a Tagline?

A tagline is a short phrase that captures a company's brand essence, personality and positioning. It helps distinguish a brand from its competitors and communicates what the brand represents and delivers.

Although taglines may appear simple, an effective tagline is usually the result of a strategic and creative process rather than an arbitrary phrase.

Why Is a Tagline Important?

A well-developed tagline can become a shorthand expression of what a brand stands for. It gives customers a concise way to recognise and remember the brand and can reinforce its positioning across different communication channels.

Brand Recognition

A memorable tagline can strengthen brand recognition by consistently associating a distinctive phrase with the brand.

Brand Differentiation

A tagline can communicate an idea, promise or characteristic that helps distinguish a brand from competitors.

Communicating Brand Positioning

An effective tagline expresses an aspect of the brand's positioning in a concise and accessible way.

Building Brand Memory

The best taglines are meaningful and memorable. Consistent use over time can help a tagline become strongly associated with the brand.

What Makes a Good Tagline?

An effective tagline should be more than simply catchy. It should reflect the brand's strategic direction and communicate an idea that is relevant to its audience.

Strong taglines are generally:

• Meaningful
• Memorable
• Distinctive
• Consistent with the brand
• Relevant to the brand's positioning
• Capable of remaining effective over time

Taglines and Brand Strategy

A tagline should grow from the wider brand strategy rather than being developed independently. It should support the brand's personality, positioning and overall identity.

For cosmetic brands, a tagline can be particularly useful for communicating a distinctive philosophy, product promise or emotional positioning in a highly competitive market.

Taglines and Brand Identity

Taglines form part of the broader brand identity and communication system. They can be used alongside the brand name, visual identity, packaging, advertising and other communication elements to create a consistent brand experience.

Historically, taglines were often developed as the central message of advertising campaigns and could have relatively short lifespans. The strongest taglines, however, can transcend individual campaigns and remain relevant despite changes in the marketplace and lifestyle.

References

Source: Designing Brand Identity – Alina Wheeler.

What Is Crambe Abyssinica Seed Oil?

Crambe Abyssinica, commonly known as Abyssinian Kale, is a herbaceous annual plant native to the Mediterranean region. The plant has also spread through Southwest Asia, Western Europe and other parts of the world.

The seeds contain approximately 30% oil. Crambe Abyssinica Seed Oil has a distinctive fatty acid profile characterised by high levels of long-chain C20–C24 fatty acids, including gondoic, behenic, erucic and nervonic acids.

The oil has a light-yellow colour, a mild nutty odour and good oxidative stability.

Key Properties of Abyssinian Kale Oil

Rich in Long-Chain Fatty Acids

The high content of long-chain fatty acids distinguishes Abyssinian Kale Oil from many other vegetable oils. This composition contributes to its characteristic sensory and formulation properties.

Excellent Slip and Spreadability

Crambe Abyssinica Seed Oil provides good slip and spreadability, making it useful in formulations where smooth application and a pleasant skin or hair feel are desired.

Good Oxidative Stability

The oil's good oxidative stability is an advantageous property when selecting vegetable oils for cosmetic formulations.

Cosmetic Applications

Haircare Products

Abyssinian Kale Oil is particularly suitable for hair cleansing and conditioning products. Its slip and spreading properties can contribute to smoother-feeling, shinier and more manageable hair.

Lip Products

The oil is well suited to decorative cosmetics, particularly lip products where smooth application, slip and spreadability are important.

Skincare Products

Crambe Abyssinica Seed Oil can also be incorporated into skincare formulations for its emollient properties, helping to provide a smooth and conditioned skin feel.

Why Use Crambe Abyssinica Seed Oil in Cosmetic Formulations?

Crambe Abyssinica Seed Oil combines a distinctive long-chain fatty acid profile with good oxidative stability, slip and spreadability. These properties make it particularly interesting for haircare and lip formulations, while its emollient characteristics also support its use in skincare products.

Ingredient Information

CAS: 91771-32-3
EINECS/EC: 294-419-5

References

Source: Modern Cosmetics – Dr. Damjan Janeš and Dr. Nina Kočevar Glavač.

What Is a Cosmetic Leak Test?

A cosmetic leak test is a packaging integrity test used to determine whether a cosmetic product and its packaging are sufficiently sealed and resistant to leakage.

The test evaluates whether the packaging can maintain its intended seal under defined conditions. A packaging failure may result in product leakage, loss of volatile ingredients, evaporation, contamination or deterioration of the product during storage and use.

Leak testing is therefore an important part of cosmetic packaging development and quality control.

Why Is Leak Testing Important for Cosmetic Products?

Cosmetic packaging does more than simply contain the product. It also needs to protect the formulation from external influences and prevent the product from escaping from the package.

A defective seal, closure or component can create problems even when the formulation itself is stable.

Preventing Product Leakage

The most obvious purpose of a leak test is to identify packaging that allows the product to escape.

Leakage can result in:

• Product loss
• Contamination of surrounding packaging
• Damaged cartons or labels
• Poor consumer experience
• Transport and storage problems

Protecting the Product from Contamination

A package that does not seal correctly can potentially allow external contaminants to enter the product.

This is particularly relevant for products where maintaining microbiological quality depends partly on limiting exposure to the external environment.

Preventing Evaporation and Product Loss

For formulations containing water, alcohol or other volatile components, inadequate packaging integrity can contribute to evaporation or changes in product composition.

An effective package helps maintain the intended formulation throughout storage and use.

Supporting Product Shelf Life

Packaging integrity is an important consideration when assessing whether a cosmetic product can maintain its intended quality throughout its shelf life.

The formulation and packaging should therefore be evaluated as an integrated system.

How Does a Cosmetic Leak Test Work?

One common approach is to pressurise the package and monitor whether the pressure changes over a defined period.

If the package is properly sealed, the pressure should remain within the expected range.

If there is a leak, pressure can escape from the package, resulting in a measurable pressure drop.

The rate and magnitude of the pressure change can therefore be used to determine whether the package meets the defined leak-tightness specification.

Differential Pressure Decay Leak Testing

A differential pressure decay leak tester is one method that can be used for packaging leak testing.

The basic principle involves:

1. Sealing or connecting the package to the test system.
2. Pressurising the package or test chamber to a defined pressure.
3. Allowing the system to stabilise.
4. Monitoring the pressure for a defined period.
5. Measuring any pressure decrease.
6. Comparing the result with the predefined acceptance criteria.

A package with a significant leak will generally show a faster or greater pressure decrease than an intact package.

The exact test pressure, stabilisation period, measurement time and acceptable pressure loss depend on the packaging type and the specifications established for the particular product.

What Packaging Can Be Leak Tested?

Leak testing can be relevant to many different cosmetic packaging formats.

Bottles

Bottles containing liquids, lotions, shampoos or other formulations can be evaluated for leakage around closures, necks, pumps and other components.

Tubes

Tubes can be tested for leakage around the tube seal, cap and dispensing area.

Jars

For jars, particular attention may be given to the closure and sealing interface, especially where the packaging is intended to prevent product loss or external contamination.

Pumps and Dispensing Systems

Pump packaging can require evaluation of the connection between the pump, closure and container.

Airless Packaging

Airless systems contain several interacting components and may require specific packaging integrity and functional testing to ensure that the dispensing system performs correctly.

Sachets and Single-Use Packaging

Flexible and single-use packaging can also require leak or seal integrity testing, particularly where the product depends on a reliable heat seal or other sealing process.

Common Causes of Cosmetic Packaging Leaks

A leak can originate from different parts of the packaging system.

Potential causes include:

Defective Seals

A poorly formed or damaged seal can allow air or product to pass through the package.

Incorrect Closure Torque

For screw-cap packaging, incorrect closure torque can compromise the seal. Both insufficient and excessive torque can potentially create packaging problems.

Damaged Components

Cracks, deformation or manufacturing defects in bottles, caps, tubes or other components can result in leakage.

Poor Component Compatibility

The formulation may interact with packaging materials or components over time, potentially affecting their physical properties or the integrity of the seal.

Manufacturing Variability

Changes in filling, capping, sealing or assembly processes can influence packaging integrity from batch to batch.

Leak Testing During Cosmetic Product Development

Leak testing should ideally be considered during packaging development rather than only after a final package has been selected.

The formulation, primary packaging and closure system should be evaluated together because the interaction between them can influence packaging performance.

During development, testing can help identify:

• Packaging design weaknesses
• Closure problems
• Seal defects
• Component compatibility issues
• Manufacturing tolerances
• Potential transport-related failures

Identifying these problems early can prevent costly packaging changes later in the product-development process.

Leak Testing and Packaging Compatibility

A cosmetic formulation can interact with its packaging over time.

Ingredients such as oils, solvents, alcohols, surfactants and other formulation components may affect certain packaging materials or sealing components.

For this reason, leak testing can be combined with broader packaging compatibility and stability studies.

The objective is not simply to confirm that a newly assembled package does not leak immediately, but to understand whether the packaging maintains its integrity throughout the expected storage and use conditions.

Leak Testing Under Stress Conditions

Depending on the product and packaging system, leak testing may also form part of a broader packaging evaluation programme.

Potential stress factors can include:

• Temperature changes
• Transportation
• Vibration
• Pressure changes
• Long-term storage
• Repeated consumer handling
• Orientation changes during storage

A package that passes an initial leak test may still require additional evaluation if it will be exposed to demanding transportation or storage conditions.

Leak Test vs. Packaging Stability Testing

A leak test and a packaging stability study are related but do not answer exactly the same question.

Leak Test

A leak test primarily evaluates whether the package has an unacceptable loss of integrity under defined test conditions.

Packaging Stability Testing

Packaging stability or compatibility testing evaluates how the formulation and packaging behave together over time and under defined environmental conditions.

A comprehensive packaging-development programme may therefore use both approaches.

Acceptance Criteria for a Leak Test

A leak test requires predefined acceptance criteria.

These criteria may be based on parameters such as:

• Maximum permitted pressure loss
• Test pressure
• Test duration
• Package volume
• Packaging material
• Closure type
• Intended product use
• Expected transport conditions

The acceptance limit should be established according to the characteristics and intended application of the specific packaging system.

There is therefore no single universal pressure-drop value that can be applied to every cosmetic package.

Leak Testing in Cosmetic Quality Control

Once a packaging system has been developed and validated, leak testing can also become part of quality-control procedures.

Quality-control testing can help identify manufacturing defects before products are released to the market.

Depending on the manufacturing process and risk assessment, testing may be performed on defined samples from production batches rather than necessarily on every individual package.

The appropriate sampling and acceptance criteria should be defined as part of the manufacturer's quality system.

Why Leak Testing Matters

A cosmetic product can have a well-developed formulation and still experience serious quality problems if its packaging does not perform correctly.

Leak testing helps verify that the packaging system can contain the product and maintain its intended integrity.

For professional cosmetic product development, leak testing can therefore support:

• Packaging selection
• Packaging development
• Formula-packaging compatibility
• Manufacturing quality control
• Product transportation
• Product shelf life
• Consumer safety and experience

Ultimately, the goal is to ensure that the formulation and packaging work together as a reliable product system from manufacturing through storage, transportation and consumer use.

What Is a Cosmetic Challenge Test?

A cosmetic challenge test, also known as a preservative efficacy test (PET), is a microbiological test used to evaluate the effectiveness of the preservation system in a cosmetic product.

During the test, a known quantity of selected microorganisms is deliberately introduced into the cosmetic formulation. The product is then monitored at defined time points to determine whether the microorganisms are reduced, remain controlled or continue to grow.

The purpose is to demonstrate that the formulation has an adequate level of antimicrobial protection and is capable of resisting microbial contamination during its intended use.

A challenge test is particularly important for cosmetic products containing water or other ingredients that can support microbial growth. However, the need for testing should ultimately be considered as part of the product's overall microbiological risk assessment.

Why Is a Challenge Test Important?

The presence of a preservative in a cosmetic formulation does not automatically mean that the finished product is adequately preserved.

The effectiveness of a preservation system depends on the complete formulation, including factors such as pH, water availability, raw materials, emulsifiers, surfactants, packaging and the interaction between the preservative and other ingredients.

A preservative system that performs well in one formulation may therefore perform differently in another.

The challenge test provides practical evidence of how the preservation system performs in the finished formulation.

Evaluating Preservative Efficacy

The primary purpose of the test is to determine whether the selected preservation system can control the microorganisms introduced into the product.

Supporting Microbiological Safety

Microbial contamination can cause deterioration of a cosmetic product and may present a safety concern. Effective antimicrobial protection helps minimise this risk.

Supporting Product Stability

Microbial growth can change the appearance, odour, texture and other characteristics of a formulation. Effective preservation helps maintain product quality during its intended shelf life.

Supporting Formulation Development

Challenge testing is not only a final quality-control exercise. It can also be an important formulation-development tool, allowing the formulator to identify preservation problems while there is still an opportunity to modify the formula.

How Does a Cosmetic Challenge Test Work?

The basic principle is relatively straightforward.

A defined quantity of selected microorganisms is introduced into separate samples of the cosmetic product. Samples are then examined at predetermined time points to determine the number of microorganisms that remain viable.

The results are expressed as changes in microbial counts, commonly as logarithmic reductions.

The greater the reduction in microbial numbers, and the longer that reduction is maintained without subsequent growth, the stronger the demonstrated antimicrobial protection.

ISO 11930 describes a reference approach for evaluating the antimicrobial protection of cosmetic products and includes a preservation efficacy test as well as an overall assessment of antimicrobial protection.

Which Microorganisms Are Tested?

The challenge test uses microorganisms representative of the main groups of microorganisms that may contaminate cosmetic products.

The original A&T formulation describes four representative groups:

Gram-Negative Bacteria

Pseudomonas aeruginosa is used as a representative Gram-negative bacterium and is particularly relevant to the microbiological evaluation of water-containing cosmetic products.

Gram-Positive Bacteria

Staphylococcus aureus represents Gram-positive bacteria and is included to evaluate the preservation system against this group of microorganisms.

Yeasts

Candida albicans represents yeast contamination.

Moulds

Aspergillus brasiliensis represents mould contamination.

Current ISO 11930 methodology also identifies these microorganisms as reference strains for preservation efficacy testing. Some testing programmes may include additional microorganisms when justified by the characteristics or risk profile of a particular product.

Microbial Inoculation and Monitoring

The microorganisms are introduced into the product as calibrated inocula. Each microorganism is generally evaluated separately so that the response of the preservation system against different microbial groups can be assessed.

The samples are then stored under controlled conditions and examined at defined intervals.

Microbial counts are determined at these time points and compared with the initial inoculum.

The resulting data show whether the microorganism population:

• decreases,
• remains controlled, or
• increases during the test period.

This is important because a preservation system should not merely produce an initial reduction in microbial numbers. It must also prevent subsequent recovery and growth during the evaluation period.

Log Reduction in Challenge Testing

Challenge-test results are commonly expressed as log reductions.

A log reduction describes the decrease in the number of viable microorganisms compared with the initial microbial count.

For example, a:

• 1-log reduction corresponds to a 90% reduction,
• 2-log reduction corresponds to a 99% reduction,
• 3-log reduction corresponds to a 99.9% reduction.

This provides a quantitative way of assessing the performance of the preservation system.

The required reduction depends on the microorganism and the test criteria being applied.

Challenge Test Acceptance Criteria

Different standards and methods can use different acceptance criteria. The original A&T content describes the Ph. Eur. criteria and distinguishes between the more stringent A criteria and the less stringent B criteria.

Under the criteria described in the original A&T content, bacteria must show at least a 2-log reduction within 2 days and a 3-log reduction within 7 days, with no subsequent increase in microbial numbers through the later observation points.

For fungi, the original criteria require at least a 2-log reduction within 7 days, again with no subsequent increase through the end of the evaluation period.

The exact acceptance criteria should always be interpreted according to the specific standard and test method used for the product. ISO 11930 provides its own evaluation framework for preservation efficacy and overall antimicrobial protection.

ISO 11930 and Cosmetic Challenge Testing

ISO 11930 – Cosmetics — Microbiology — Evaluation of the antimicrobial protection of a cosmetic product is one of the key international standards used when evaluating the preservation of cosmetic products.

The standard describes a preservation efficacy test and a procedure for evaluating the overall antimicrobial protection of a cosmetic product.

Importantly, antimicrobial protection does not necessarily come only from the chemical preservative. ISO 11930 recognises that protection can also be influenced by:

• The formulation itself
• The preservation system
• Packaging design
• Manufacturing conditions
• The overall microbiological risk of the product

This means that preservation should be considered as a complete system rather than simply as the presence or absence of a particular preservative.

Which Cosmetic Products May Require Challenge Testing?

Challenge testing is particularly relevant to cosmetic formulations that contain water and are potentially susceptible to microbial growth.

Examples include:

Creams and Lotions

Emulsions containing an aqueous phase generally require careful consideration of their preservation system.

Serums and Gels

Water-based serums and gels can provide favourable conditions for microbial growth if they are not adequately protected.

Shampoos and Shower Gels

These products often contain substantial amounts of water and therefore require appropriate microbiological protection.

Liquid Cleansers

Water-based cleansing products can also require effective preservation depending on their composition and packaging.

Other Water-Containing Products

Many other cosmetic formulations may require challenge testing depending on their microbiological risk profile.

Not every cosmetic product necessarily requires a conventional challenge test. ISO 11930 specifically provides for products that have been determined to have a sufficiently low microbiological risk according to the relevant risk-assessment approach.

Challenge Testing During Cosmetic Product Development

One of the most important reasons to perform a challenge test is to identify preservation problems before the formulation is finalised.

A formulation may appear completely satisfactory during development while still having inadequate microbiological protection.

Challenge testing can therefore be incorporated into the development process alongside other formulation and stability evaluations.

If the formulation fails the test, the formulator may need to investigate factors such as:

Preservative Selection

The selected preservative or preservative combination may not provide sufficient broad-spectrum protection for the formulation.

Preservative Concentration

The concentration may be insufficient under the specific formulation conditions.

pH

The activity of certain preservatives can depend strongly on formulation pH.

Ingredient Interactions

Other ingredients can affect the availability or effectiveness of a preservative.

Packaging

The packaging system can influence the level of microbial exposure during consumer use.

A challenge-test failure therefore provides valuable information for formulation optimisation rather than simply indicating that the product cannot be developed.

Challenge Test and Packaging

Packaging is an important part of the overall microbiological protection of a cosmetic product.

A product used repeatedly by consumers may be exposed to microorganisms during normal handling. The design of the package can influence how much opportunity there is for contamination.

Examples of packaging considerations include:

• Open jars
• Pumps
• Airless systems
• Single-use packaging
• Applicator systems

The formulation and packaging should therefore be considered together when assessing the microbiological protection of the final cosmetic product.

ISO 11930 includes consideration of packaging characteristics as part of the overall evaluation of antimicrobial protection.

Challenge Test vs. Microbiological Quality Testing

A challenge test should not be confused with routine microbiological quality testing.

Microbiological Quality Testing

Routine microbiological testing evaluates whether microorganisms are present in a production sample and whether the product meets defined microbiological quality requirements.

Challenge Testing

A challenge test deliberately introduces selected microorganisms into the formulation to evaluate the effectiveness of the preservation system.

The two tests therefore answer different questions and can form complementary parts of a cosmetic product's microbiological quality and safety strategy.

What Happens If a Cosmetic Fails the Challenge Test?

A failed challenge test does not necessarily mean that the entire product concept must be abandoned.

Instead, the result can help identify weaknesses in the preservation system.

Depending on the formulation, possible development actions may include:

• Changing the preservative system
• Optimising preservative concentration
• Adjusting the formulation pH
• Modifying the formulation composition
• Introducing synergistic antimicrobial ingredients where appropriate
• Reviewing manufacturing conditions
• Changing the packaging system
• Repeating the challenge test after reformulation

The reformulated product should then be appropriately re-evaluated to demonstrate that the revised preservation system provides sufficient protection.

Challenge Testing and Cosmetic Product Safety

Preservation is an important part of cosmetic microbiological safety, but it should not be considered in isolation.

A complete microbiological risk assessment can consider:

• Raw material microbiological quality
• Manufacturing hygiene
• Water quality
• Product formulation
• pH and water availability
• Preservation system
• Packaging
• Intended consumer use
• Product application area
• Expected shelf life

ISO 11930 explicitly places preservation efficacy testing within the broader evaluation of the overall antimicrobial protection of a cosmetic product.

When Is a Challenge Test Not Necessary?

A conventional challenge test is not necessarily required for every cosmetic product. The need for preservative efficacy testing should be determined as part of the product's microbiological risk assessment, taking into account the formulation, packaging, manufacturing process and intended use.

ISO 11930 recognises that some cosmetic products may have a sufficiently low microbiological risk that a conventional preservation efficacy test is not required. However, this conclusion should be supported by a documented and scientifically justified assessment rather than simply assuming that a product does not need testing.

Anhydrous Products

Products containing no water, or only negligible amounts of water that are not available to support microbial growth, may have a low microbiological risk.

Examples can include certain:

• Anhydrous oils
• Oil-based balms
• Some lip products
• Certain wax-based products

However, the absence of added water alone does not automatically mean that microbiological risk is zero. The complete formulation and manufacturing conditions should still be evaluated.

Products with Very Low Water Availability

Some formulations may contain water but have conditions that make microbial growth highly unlikely. Low water activity (aw) can significantly limit the ability of microorganisms to grow.

In these cases, the microbiological risk assessment may provide sufficient justification for not performing a conventional challenge test.

Products with Extreme pH

Formulations with a sufficiently low or high pH may create an environment that is unfavourable for the growth of many microorganisms.

However, pH alone should not automatically be used as justification for omitting a challenge test. The resistance of different microorganisms to the specific formulation conditions and the complete product composition should be considered.

Products with High Alcohol Content

Certain products containing a sufficiently high concentration of alcohol can have a low microbiological risk because the formulation itself provides antimicrobial protection.

Examples may include some alcohol-based products and specific hydroalcoholic formulations.

The actual alcohol concentration and the complete formulation need to be assessed before concluding that conventional challenge testing is unnecessary.

Products in Protective or Single-Use Packaging

Packaging can significantly reduce the possibility of microbial contamination during consumer use.

Examples include:

• Single-dose products
• Individually packaged products
• Certain airless dispensing systems
• Packaging systems that minimise repeated contact with the formulation

Nevertheless, packaging should be considered as one element of the microbiological risk assessment, rather than automatically replacing preservation efficacy testing.

Products with an Inherently Low Microbiological Risk

Some products may have a combination of characteristics that makes microbial growth unlikely. This can include a combination of low water availability, an unfavourable pH, antimicrobial formulation characteristics and protective packaging.

For such products, a documented risk assessment may conclude that a conventional challenge test is not necessary.

When Can a Challenge Test Be Omitted?

The important principle is that a challenge test should not be omitted simply because a product appears unlikely to support microbial growth.

Instead, the decision should be based on a documented microbiological risk assessment demonstrating why the product has sufficiently low microbiological risk.

Factors that may be considered include:

• Water content and water activity
• Formulation pH
• Alcohol concentration
• Presence of ingredients with antimicrobial properties
• Product composition
• Packaging design
• Manufacturing conditions
• Intended method of application
• Frequency of consumer use
• Risk of contamination during use
• Product's intended area of application

If the overall assessment demonstrates that the product has a sufficiently low microbiological risk, a conventional preservative efficacy test may not be necessary.

Low-Risk Does Not Mean No Microbiological Testing

It is important to distinguish between not requiring a challenge test and not requiring microbiological evaluation at all.

Even when a product is considered low risk, other aspects of microbiological quality may still need to be assessed as part of the product safety and quality-control process.

The decision to omit challenge testing should therefore be supported by appropriate technical justification and documented within the product development and safety documentation.

Challenge Test or Risk Assessment?

The decision can essentially be viewed as two different approaches:

Products with a meaningful microbiological risk:
A preservative efficacy/challenge test can be used to demonstrate that the formulation provides adequate antimicrobial protection.

Products with sufficiently low microbiological risk:
A scientifically justified microbiological risk assessment may demonstrate that a conventional challenge test is not necessary.

This distinction is particularly important during professional cosmetic formulation because the objective is not simply to include a preservative or perform a test, but to demonstrate that the finished product has an appropriate level of microbiological protection for its intended use.

A challenge test is therefore an important tool, but it is not a universal requirement for every cosmetic formulation.

Why Challenge Testing Matters in Professional Cosmetic Formulation

A cosmetic formula can have excellent texture, appearance, stability and sensory performance and still be unsuitable for launch if its microbiological protection is inadequate.

Challenge testing provides evidence that the preservation system works within the actual formulation, rather than simply assuming that a particular preservative will be effective because it is commonly used.

For professional cosmetic development, this makes challenge testing an important tool for:

• Preservative selection
• Formula optimisation
• Microbiological risk management
• Product safety
• Shelf-life development
• Packaging decisions
• Regulatory and safety documentation

A well-designed preservation strategy, supported by appropriate microbiological testing, helps ensure that the finished cosmetic product remains adequately protected throughout its intended period of use.

References

Source: Cosmetic Formulation Principles and Practice – Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters.

What Is a Preservative?

A preservative is a substance used to kill or prevent the growth of microorganisms which, through their growth, could spoil or contaminate a raw material or finished product.

In cosmetic formulation, preservatives are particularly important for products that contain water or other ingredients that can support microbial growth. An appropriate preservation system helps protect the formulation throughout its intended shelf life and during normal consumer use.

Why Are Preservatives Important in Cosmetics?

Cosmetic products can become contaminated with microorganisms during manufacturing, filling, storage and consumer use. Water-containing formulations can provide an environment in which bacteria, yeasts and moulds may grow if the product is not adequately protected.

Preservation is therefore an important part of cosmetic product development. The objective is to control microbial growth while maintaining the desired physical, chemical and sensory properties of the finished product.

Protecting the Product

An effective preservation system helps prevent microbial growth that could cause changes in the product's appearance, odour, texture or overall quality.

Supporting Product Safety

Controlling microorganisms is an important aspect of developing cosmetic products that remain suitable for their intended use throughout their shelf life.

Maintaining Product Quality

Microbial contamination can negatively affect both the formulation and the consumer experience. Appropriate preservation helps maintain product quality during storage and use.

Types of Cosmetic Preservatives

Preservatives can be divided into different groups according to their chemical structure, mechanism of action and application within a formulation.

Antimicrobial Preservatives

Antimicrobial preservatives are used to inhibit or control the growth of microorganisms such as bacteria, yeasts and moulds.

Examples of commonly used preservative systems include ingredients from different chemical families, such as organic acids, alcohols and other antimicrobial compounds.

Multifunctional Cosmetic Ingredients

Some cosmetic ingredients can provide preservation support while also contributing other formulation or sensory benefits. These ingredients may be incorporated into a broader preservation strategy rather than functioning as the sole preservative.

Preservative Systems in Cosmetic Formulation

In many formulations, preservation is not simply a matter of selecting one preservative. The complete preservation system needs to be considered in relation to the composition of the product.

Factors that can influence preservation include:

Water Content

The presence and availability of water can have a significant influence on the potential for microbial growth.

pH

The pH of a formulation can affect both microbial growth and the performance of certain preservatives. Preservative selection should therefore be compatible with the target pH of the finished product.

Packaging

Packaging can influence the amount of microbial exposure a product experiences during consumer use. Packaging design should therefore be considered alongside the preservation strategy.

Formulation Composition

Oils, surfactants, emulsifiers, botanical extracts and other ingredients can influence the distribution and effectiveness of a preservative system.

Preservatives and Different Cosmetic Formulations

The preservation requirements of a cosmetic product depend strongly on its formulation.

Emulsions

Creams and lotions commonly contain both water and oil phases and therefore require careful consideration of microbial protection.

Gels and Serums

Water-based gels and serums can also require effective preservation, depending on their composition and packaging.

Cleansing Products

Shower gels, liquid cleansers and shampoos often contain significant amounts of water and require an appropriate preservation strategy.

Anhydrous Products

Products with little or no available water generally present different preservation considerations from conventional water-based formulations. However, the complete formulation and manufacturing process still need to be assessed.

Choosing a Preservative for a Cosmetic Formula

Selecting a preservative should be part of the overall formulation development process rather than an isolated decision.

The formulator needs to consider:

• The type of cosmetic product
• Water content and water availability
• Target pH
• Ingredient compatibility
• Packaging system
• Manufacturing process
• Intended shelf life
• Expected consumer use
• Regulatory requirements
• The required level of microbial protection

The selected preservation system should also be evaluated in the finished formulation rather than relying only on the theoretical activity of an individual ingredient.

Preservative Efficacy Testing

Preservation needs to be evaluated in the finished cosmetic formulation. Microbiological testing can be used to assess whether the preservation system provides appropriate protection against microbial contamination.

A preservative system that performs well in one formulation may not provide the same level of protection in another formula because factors such as pH, water activity, packaging and ingredient interactions can differ.

For this reason, preservative selection and testing are an important part of professional cosmetic formulation development.

Preservatives and Cosmetic Product Development

Preservation should be considered from the early stages of product development. Choosing the preservation system at an early stage allows the formulator to evaluate its compatibility with the rest of the formulation and make adjustments before the product reaches the final development stage.

A well-designed preservation strategy contributes to the development of cosmetic products that remain stable, acceptable and appropriately protected throughout their intended period of use.

References

Source: Cosmetic Formulation Principles and Practice – Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters.

What Is an Emulsion?

An emulsion is a mixture of two or more liquids that are normally immiscible, meaning they do not naturally blend together. Because of their different properties, these liquids tend to separate into distinct phases.

Emulsions belong to the broader class of two-phase systems known as colloids. The word emulsion comes from the Latin word emulgere, meaning “to milk out”, reflecting the fact that milk is a naturally occurring emulsion of fat and water.

In cosmetic formulation, emulsions make it possible to combine oil-soluble and water-soluble ingredients in a single product while creating the desired texture, appearance and sensory characteristics.

Emulsions in Cosmetic Formulation

Emulsions are among the most widely used formulation systems in cosmetics. They are found in products such as:

• Creams
• Lotions
• Facial moisturisers
• Body lotions
• Sunscreens
• Cleansing products
• Haircare products

The ability to combine aqueous and oily ingredients gives formulators considerable flexibility when designing products with different textures, application characteristics and skin-conditioning properties.

Types of Cosmetic Emulsions

Cosmetic emulsions are generally classified according to which phase is dispersed and which phase forms the continuous matrix.

Oil-in-Water (O/W) Emulsions

In an oil-in-water emulsion, small oil droplets are dispersed throughout a continuous aqueous phase.

O/W emulsions are widely used for lotions, lighter creams and other formulations where a lighter, more easily spreadable sensory profile is desired.

Water-in-Oil (W/O) Emulsions

In a water-in-oil emulsion, water droplets are dispersed throughout a continuous oil phase.

W/O emulsions can provide a richer and more occlusive sensory profile and can be useful when developing products where a stronger oil-phase character is required.

How Are Emulsions Stabilised?

Because oil and water naturally tend to separate, an emulsion requires an appropriate stabilisation system.

A balanced surfactant or emulsifier system can help incorporate oils into an aqueous phase and maintain the interface between the two phases.

In cosmetic formulations, non-ionic surfactants and emulsifiers can be used for this purpose. Examples include:

• Polyglycerol esters
• Fatty alcohol ethoxylates
• Monoglycerides
• Sucrose esters
• Sorbitan esters
• Polymers
• Combinations of emulsifiers and stabilisers

The choice and balance of the emulsifying system are important factors in achieving a stable and aesthetically pleasing formulation.

The Role of Emulsifiers

Emulsifiers contain chemical characteristics that allow them to interact with both the aqueous and oil phases.

An emulsifier system associates primarily with either the oil or aqueous phase while having sufficient polarity to locate at the interface between the two phases.

By concentrating at this interface, the emulsifier helps reduce the tendency of the dispersed droplets to separate and supports the formation of a stable emulsion.

The Hydrophilic-Lipophilic Balance (HLB) System

The hydrophilic-lipophilic balance, commonly referred to as the HLB system, is an important concept in emulsion formulation.

It describes the relative affinity of an emulsifier for water and oil. Selecting emulsifiers with an appropriate balance of hydrophilic and lipophilic properties can help formulators develop stable oil-in-water or water-in-oil systems.

The HLB system can therefore be used as one of the tools for selecting and combining emulsifiers during cosmetic formulation development.

Emulsion Stability in Cosmetic Products

A successful cosmetic emulsion needs to remain sufficiently stable throughout its intended storage and use period.

Stability can be influenced by several factors, including:

Emulsifier Selection

The type and concentration of emulsifier can have a significant effect on the stability and physical characteristics of the finished formulation.

Oil and Water Phase Composition

The composition and ratio of the oil and aqueous phases influence the structure, viscosity and sensory properties of an emulsion.

Emulsifier and Stabiliser Combinations

Combining emulsifiers with appropriate stabilisers or polymers can help improve the physical stability of the formulation.

Processing Conditions

The way an emulsion is manufactured, including the order of addition, temperature and mixing conditions, can influence droplet formation and the final structure of the product.

Emulsions and Cosmetic Product Development

Developing an emulsion involves more than simply combining oil, water and an emulsifier. The formulation needs to be designed around the desired product characteristics, ingredient compatibility and stability requirements.

The formulator must consider:

• The desired emulsion type
• Oil and water phase composition
• Emulsifier selection
• Emulsifier balance
• Stabilisation system
• Texture and viscosity
• Sensory properties
• Processing conditions
• Long-term stability
• Packaging compatibility

A carefully designed emulsifier system can therefore be central to achieving both the technical stability and the consumer experience expected from a cosmetic product.

Why Are Emulsions Important in Cosmetics?

Emulsions provide one of the most versatile ways to formulate modern cosmetic products. They allow oil-soluble and water-soluble ingredients to be incorporated into the same product while offering extensive control over texture, viscosity, application and sensory performance.

For this reason, understanding emulsion structure, emulsifier selection and stabilisation is fundamental to professional cosmetic formulation.

References

Source: Cosmetic Formulation Principles and Practice – Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters.

What Are Flavonoids?

Flavonoids are a large and diverse group of naturally occurring compounds found throughout the plant kingdom. The name comes from the Greek word flava, meaning yellow, reflecting the characteristic colour of many flavonoid compounds. The collective name “flavonoids” was proposed by Geissman in 1952.

Flavonoids are structurally related compounds that are often classified as polyphenols. Many have a basic skeleton containing 15 carbon atoms, generally consisting of a phenolic component and a cinnamic acid-derived building block.

The flavonoid family includes several structurally different groups, including flavones, flavonols, chalcones, catechins and anthocyanidins. Their chemical diversity contributes to their wide range of functions and applications in cosmetic formulations.

Antioxidant Properties of Flavonoids

One of the most important properties of flavonoids in cosmetic applications is their antioxidant activity.

Certain flavonoids can help scavenge free radicals and provide antioxidant protection. This property is particularly relevant to skincare because oxidative stress can contribute to changes in the appearance and condition of skin cells.

Flavonoids in Red Wine

Flavonoids found in red wine derived from Vitis vinifera, including quercetin, kaempferol and anthocyanidins, are associated with free radical-scavenging activity.

Flavonoids in Green Tea

Green tea (Camellia sinensis, also known as Thea viridis) contains flavonoid compounds including catechins and catechin gallate esters. These compounds have demonstrated antioxidant activity against free radicals.

The antioxidant properties of these plant-derived compounds have been recognised through dietary use for generations, while similar antioxidant activity has also been observed when certain flavonoid-containing materials are applied topically in cosmetic formulations.

Flavonoids and Skin Protection

The antioxidant properties of flavonoids make them relevant to cosmetic formulations designed to support skin exposed to environmental stress.

By incorporating flavonoid-rich botanical extracts into skincare products, formulators can take advantage of naturally occurring antioxidant compounds while also benefiting from the additional properties of the botanical source.

Flavonoids are therefore commonly considered when developing formulations focused on antioxidant skincare and maintaining the appearance of healthy, protected skin.

Flavonoids as Natural Colourants

In addition to their antioxidant properties, flavonoids can contribute natural colour to cosmetic ingredients and botanical extracts.

Different groups of flavonoids can produce a range of colours:

Chalcones and Flavonols

Chalcones and flavonols can contribute yellow colours and are therefore of interest as potential sources of natural colour in cosmetics and toiletries.

Anthocyanidins

Anthocyanidins are responsible for red, blue and violet colours found in many plants. Their natural pigmentation makes anthocyanidin-containing botanical materials particularly interesting for applications where naturally derived colour is desired.

Flavones

Flavones are generally colourless, but they can strongly absorb ultraviolet radiation. In plants, this property contributes to their role in interactions with pollinating insects.

The use of flavonoid-containing materials as natural colour sources in cosmetics and toiletries continues to develop, although their relatively poor light stability can present a formulation challenge.

Flavonoid Glycosides and Aglycones

Flavonoids may occur naturally in plants as glycosides or as aglycones.

Flavonoid Glycosides

Glycosides are flavonoid molecules in which one or more hydroxyl groups are substituted with a sugar component. These sugars can include galactose, glucose, mannose and rhamnose.

Aglycones

Aglycones are flavonoid molecules that do not contain a sugar moiety.

This distinction is important when working with botanical extracts because the chemical form of a flavonoid can influence its properties and behaviour within a cosmetic formulation.

Cosmetic Applications of Flavonoids

Flavonoids can be incorporated into cosmetic formulations through purified ingredients or, more commonly, through botanical extracts naturally containing flavonoid compounds.

Antioxidant Skincare

Flavonoid-rich botanical extracts can be used in facial creams, serums, lotions and other skincare products designed around antioxidant properties.

Green Tea-Based Formulations

Green tea extracts containing catechins and other polyphenolic compounds are widely relevant to cosmetic formulations where antioxidant properties are desired.

Botanical Skincare

Flavonoid-containing plant extracts can be incorporated into formulations that combine antioxidant properties with the broader sensory and skin-conditioning characteristics of botanical ingredients.

Natural Colour Cosmetics

Selected flavonoid-containing materials can also be explored as naturally derived colour sources for cosmetics and toiletries, although light stability must be considered during formulation development.

Formulation Considerations for Flavonoids

When incorporating flavonoid-rich ingredients into cosmetic formulations, their chemical structure, source and stability should be considered carefully.

Light stability can be particularly important when flavonoid-containing materials are being used for their colour. The stability of the specific extract or isolated compound should therefore be evaluated under the intended formulation and packaging conditions.

The final performance of a flavonoid-containing ingredient will also depend on the botanical source, extraction process, concentration and overall formulation environment.

Why Use Flavonoids in Cosmetic Formulations?

Flavonoids are valuable cosmetic ingredients because they combine several interesting properties within a diverse family of naturally occurring compounds.

Their main areas of interest include:

• Antioxidant activity
• Free radical-scavenging properties
• Support for skin exposed to environmental stress
• Natural colour potential
• Compatibility with botanical and plant-derived cosmetic concepts

Their diversity also allows formulators to select different flavonoid-containing botanical sources according to the desired positioning and performance characteristics of the finished product.

Flavonoids in Cosmetic Product Development

For cosmetic product development, flavonoids can be particularly useful when developing products based on botanical, antioxidant or naturally derived ingredient concepts.

The choice of flavonoid source should take into account the intended cosmetic benefit, extract composition, stability, colour, formulation compatibility and packaging requirements.

References

Source: Dermatologic, Cosmeceutic and Cosmetic development – Kenneth A. Walters, Michael S. Roberts.

What Are Fatty Acids?

Fatty acids are organic compounds that form important components of many vegetable oils and other lipid-based cosmetic ingredients. Vegetable, nut, seed and kernel oils are often complex mixtures containing fatty acids with different carbon chain lengths and compositions.

In cosmetic formulation, the fatty acid profile of an oil has a significant influence on its properties and potential applications. Different oils can therefore provide different levels of emollience, occlusivity, skin conditioning and sensory performance.

Fixed vegetable oils are among the simplest and most established approaches for improving the feel and appearance of dry skin.

Fatty Acids and Dry Skin

Occlusive Properties

Many vegetable oils can form a protective layer over the skin surface. This occlusive effect can help slow transepidermal water loss (TEWL), allowing more water to remain within the stratum corneum and upper layers of the skin.

The degree of occlusivity varies between oils and is influenced by their composition and physical characteristics.

Supporting Skin Hydration

By reducing water loss from the skin surface, occlusive oils can help support hydration within the stratum corneum. This can be particularly useful in formulations designed for dry or dehydrated skin.

Improving the Appearance of Rough Skin

Vegetable oils can also help improve the appearance and feel of dry, desquamating skin. By coating the skin surface and helping to smooth down loose skin cells, they can make rough or scaly skin appear softer and more even.

Vegetable Oils Rich in Fatty Acids

Coconut, Sunflower, Safflower, Rapeseed and Sesame Oils

Coconut, sunflower, safflower, rapeseed and sesame seed oils are examples of fixed vegetable oils commonly used in cosmetic formulations.

These oils can provide effective skin coverage and are frequently used as carrier oils, including as carriers for essential oils. Their ability to coat and condition the skin also makes them useful in formulations targeting dryness and skin comfort.

Castor Seed Oil

Castor seed oil, derived from Ricinus communis, is particularly notable for its high gloss and strong occlusive properties.

Its high gloss makes it a frequent component of lipsticks and lip salves, while its occlusive characteristics make it useful in protective skincare formulations. A traditional example is zinc and castor oil cream, which has historically been used in products for protecting the skin in areas such as the nappy or diaper area.

Evening Primrose Oil

Evening primrose oil, derived from Oenothera biennis, is notable for its content of gamma-linolenic acid (γ-linolenic acid).

Its fatty acid composition makes it an interesting ingredient for cosmetic formulations focused on skin conditioning and emollience.

Borage Seed Oil

Borage or starflower seed oil, derived from Borago officinalis, is another vegetable oil particularly rich in gamma-linolenic acid.

This makes it a useful source of this fatty acid in cosmetic formulations and an interesting option for products designed around skin conditioning.

Blackcurrant Seed Oil

Blackcurrant seed oil, derived from Ribes nigrum, is also notable for its gamma-linolenic acid content.

Its fatty acid profile makes it suitable for formulations where a specialised plant oil is desired for its emollient and conditioning characteristics.

Specialty Vegetable Oils

Inchi Oil

Inchi oil, derived from Plukenetia volubilis, became commercially available as a cosmetic oil in the mid-2000s. It is also known as Sacha Inchi or Aztec peanut, although it is botanically unrelated to the peanut (Arachis hypogaea).

The oil is rich in polyunsaturated fatty acids, including omega-3 and omega-6 fatty acids, which make it an interesting ingredient for cosmetic skincare formulations.

Rose Hip Seed Oil

Certain rose hip seed oils, including oil obtained from Rosa aff. rubiginosa, are known for their fatty acid content and traditional use in skincare.

The original A&T Formulation content notes that some references associate this oil with vitamin A and reports anecdotal clinical evidence relating to skin elasticity and the appearance of hyperpigmented scar tissue.

These traditional and reported uses make rose hip seed oil an interesting ingredient for cosmetic formulations targeting skin conditioning and the appearance of uneven or aged skin.

Choosing Fatty Acid-Rich Oils for Cosmetic Formulation

Consider the Fatty Acid Profile

The fatty acid composition of an oil is an important factor when selecting it for a cosmetic formulation. Different fatty acids and their relative proportions can influence the oil's sensory characteristics, stability and skin-conditioning properties.

Consider Oxidative Stability

Oils containing high levels of unsaturated fatty acids can be more susceptible to oxidation. Formulators therefore need to consider oxidative stability, antioxidants, packaging and processing conditions when working with these materials.

Consider the Intended Skin Benefit

The choice of vegetable oil should reflect the desired function of the finished product. Highly occlusive oils may be appropriate for protective formulations, while lighter oils may be selected where a different sensory profile is desired.

Consider the Finished Product

The same oil can behave differently depending on the overall formulation. Its interaction with emulsifiers, other oils, active ingredients and the final product structure needs to be considered during formulation development.

Fatty Acids in Cosmetic Formulation

Fatty acids and fatty-acid-rich vegetable oils provide formulators with a broad range of options for improving the sensory and functional properties of skincare products.

Their ability to condition the skin, support hydration by reducing water loss and improve the appearance of dry or rough skin makes them particularly valuable in moisturisers, protective creams, lip products, body care and other emollient formulations.

The selection of the appropriate oil should ultimately be based on its fatty acid profile, stability, sensory characteristics, intended cosmetic function and compatibility with the complete formulation.

References

Source: Dermatologic, Cosmeceutic and Cosmetic Development – Kenneth A. Walters, Michael S. Roberts.

What Is a Natural Ingredient?

A natural ingredient is a cosmetic raw material that originates from a natural source. Depending on the ingredient, the source may include plants, minerals, microorganisms or other naturally occurring materials.

Natural ingredients have been used in cosmetics for centuries, with botanical extracts, oils, waxes, clays and other naturally derived materials continuing to play an important role in modern cosmetic formulation.

However, the term "natural" can have different meanings depending on the regulatory framework, certification standard and definition being applied. The origin of a raw material alone does not necessarily describe how it has been processed or whether it meets the requirements of a particular natural cosmetics standard.

Sources of Natural Cosmetic Ingredients

Plant-Derived Ingredients

Plants are one of the most important sources of natural cosmetic ingredients. These can include botanical extracts, vegetable oils, plant butters, waxes, hydrosols and other plant-derived materials.

Examples include Aloe Vera, Oat Extract, Shea Butter and a wide range of botanical extracts used for their conditioning, moisturising, soothing or other cosmetic properties.

Mineral-Derived Ingredients

Certain minerals and naturally occurring inorganic materials can also be used in cosmetics. Examples include clays, mineral pigments and other mineral-based raw materials.

Their properties can make them particularly useful in products such as masks, colour cosmetics and cleansing formulations.

Microorganism-Derived Ingredients

Microorganisms can also be used as sources of cosmetic ingredients. Fermentation processes, for example, can produce or modify materials that are used in skincare and other cosmetic applications.

Animal-Derived Ingredients

Some natural cosmetic ingredients can originate from animal sources. However, their use depends on the formulation concept, consumer expectations, regulatory requirements and the brand's positioning.

For brands developing vegan or plant-based products, the source of every raw material needs to be evaluated carefully.

Benefits of Natural Ingredients in Cosmetics

Botanical and Natural Properties

Natural ingredients can provide a wide range of functional and cosmetic properties. Depending on the raw material, they may contribute moisturising, emollient, soothing, antioxidant, conditioning, cleansing or other benefits.

Consumer Appeal

Natural and naturally derived ingredients can be attractive to consumers who are specifically looking for products positioned around natural beauty, botanical ingredients or renewable raw materials.

For cosmetic brands, the choice of natural ingredients can therefore contribute not only to formulation performance but also to product positioning.

Formulation Diversity

The large variety of natural raw materials available to formulators provides many options for creating distinctive cosmetic formulations. Different extracts, oils, butters, waxes and other materials can be combined to create specific textures, sensory profiles and product concepts.

Natural vs. Naturally Derived Ingredients

Natural Ingredients

A natural ingredient is generally obtained from a natural source with limited chemical modification, depending on the definition or certification standard being applied.

The exact criteria can differ between standards, so "natural" should not be treated as a universally defined technical category without considering the relevant framework.

Naturally Derived Ingredients

Naturally derived ingredients originate from natural raw materials but may undergo processing or chemical modification to achieve a specific functionality or performance.

These ingredients can be particularly useful when a formulator needs a combination of natural origin and technical performance that may not be achievable with an unmodified natural raw material.

Why the Distinction Matters

The distinction between natural and naturally derived ingredients is important when developing products for markets or certifications with specific natural-origin requirements.

A formulation should therefore be evaluated ingredient by ingredient rather than assuming that every ingredient described as "plant-derived" automatically qualifies as a natural ingredient under every standard.

Formulation Considerations

Stability

Natural ingredients can sometimes present additional formulation challenges because their composition may vary according to factors such as plant variety, geographical origin, harvesting conditions and extraction method.

The stability of the finished formulation therefore needs to be evaluated carefully.

Preservation

Botanical extracts and other natural raw materials may introduce components that influence the microbiological stability of a formulation. An appropriate preservation strategy is therefore essential for water-containing cosmetic products.

Colour and Odour

Natural extracts, oils and other botanical materials can contribute their own colour and odour to a formulation. These characteristics may vary between raw material batches and need to be considered when developing the final product.

Compatibility

Natural ingredients need to be evaluated for compatibility with the other components of the formula. Their interaction with emulsifiers, surfactants, preservatives, active ingredients and packaging can influence the stability and performance of the finished product.

Natural Ingredients and Cosmetic Product Development

Ingredient Selection

Selecting a natural ingredient should involve more than considering its botanical name or marketing appeal. The formulator needs to evaluate its functionality, recommended use level, stability, quality specifications, compatibility and regulatory status.

Supplier and Raw Material Quality

The quality and consistency of natural raw materials can vary between suppliers. Standardised specifications, appropriate quality control and reliable sourcing are therefore important considerations during formulation development.

Extraction Method

The extraction method can have a significant influence on the composition and properties of a botanical ingredient. Water, glycerin, ethanol, oils and other extraction systems can produce extracts with different characteristics.

Final Product Performance

The objective is ultimately to create a finished cosmetic product that performs effectively and remains stable throughout its intended shelf life. Natural origin is one consideration within this process, but it does not replace the need for sound formulation development and testing.

Natural Ingredients and Sustainability

Renewable Sources

Many natural cosmetic ingredients are derived from renewable plant resources. When responsibly sourced, these materials can form part of a more sustainable raw material strategy.

Responsible Sourcing

The environmental and social impact of a natural ingredient depends on how and where it is produced and sourced. Factors such as cultivation, harvesting, biodiversity, water use, processing and transportation can all influence its overall sustainability profile.

Natural Does Not Automatically Mean Sustainable

A natural ingredient is not necessarily more sustainable than a synthetic alternative in every situation. Sustainability depends on the complete lifecycle of the raw material, including its production, processing, transportation, use and disposal.

For this reason, sustainability decisions should consider the full environmental impact rather than natural origin alone.

Developing Natural Cosmetic Formulations

Natural cosmetic formulation requires the same fundamental attention to product safety, stability, functionality and sensory performance as any other cosmetic formulation.

The additional challenge is selecting raw materials that meet the desired natural-origin or certification requirements while still creating a stable, effective and commercially viable product.

For brands developing natural cosmetics, early consideration of ingredient sourcing, formulation compatibility, preservation, stability and regulatory requirements can help prevent problems later in the development process.

What Is Transepidermal Water Loss?

Transepidermal Water Loss, commonly abbreviated as TEWL, describes the amount of water that evaporates from the outermost layer of the skin, known as the stratum corneum, into the surrounding environment.

TEWL is a natural physiological process. Even healthy skin continuously loses a certain amount of water to the environment. However, the rate of water loss can increase when the skin barrier is compromised or when environmental and external factors place additional stress on the skin.

Factors such as dry air, hot weather and harsh cleansing products can increase TEWL. Elevated TEWL is also commonly associated with dry skin and certain skin conditions.

TEWL and the Skin Barrier

The Role of the Stratum Corneum

The stratum corneum forms the outermost layer of the epidermis and plays an important role in limiting the loss of water from the skin.

A healthy and intact skin barrier helps regulate the movement of water between the skin and the surrounding environment. When the barrier is disrupted, water can evaporate more readily from the skin surface, resulting in increased TEWL.

TEWL as an Indicator of Barrier Function

TEWL is widely used as an objective, non-invasive measurement of the skin's barrier to evaporative water loss.

The original research history of TEWL measurements dates back to the classic experiment by Pinson in 1942, which compared insensible perspiration from corresponding skin sites with and without active sweat glands.

Today, TEWL measurements are used in dermatological and cosmetic research to evaluate changes in skin barrier function and to assess how different products or treatments affect the skin.

What Can Increase TEWL?

Dry Environmental Conditions

Dry air can increase the rate at which water evaporates from the skin. Low environmental humidity can therefore contribute to increased TEWL and a drier skin feel.

Heat

Higher temperatures can influence water evaporation from the skin and may contribute to changes in TEWL measurements.

Harsh Cleansing

Aggressive cleansing products or excessive cleansing can disturb the skin surface and its barrier properties. This may increase water loss and contribute to dry or uncomfortable skin.

Skin Barrier Disruption

Any factor that compromises the integrity of the stratum corneum can potentially increase TEWL. This is why TEWL is frequently used when evaluating the condition and recovery of the skin barrier.

How Is TEWL Measured?

TEWL is measured by assessing the amount of water vapour leaving the skin surface. The result is commonly expressed in grams per square metre per hour (g/m²/h).

Reported TEWL values can vary considerably depending on factors such as body site, environmental conditions, age and individual skin characteristics. The original A&T content gives a normal TEWL range of approximately 2.3 to 44 g/m²/h.

For TEWL to provide a meaningful indication of skin barrier function, measurements need to be performed under controlled conditions and without active sweating.

Controlled Conditions for TEWL Measurement

Temperature and Relative Humidity

TEWL measurements are typically performed in controlled temperature and humidity conditions. The original A&T content describes a typical environment of approximately 21°C and 50% relative humidity (RH).

Subjects are generally allowed to rest before measurement so that external factors such as physical activity and increased sweating do not interfere with the results.

Dry Skin Surface

The skin surface should be dry when TEWL is measured. Active sweat gland activity can affect water evaporation independently of the passive water loss associated with the skin barrier.

For this reason, TEWL is considered a true reflection of stratum corneum barrier function only when the skin surface is dry and sweat gland activity is absent or adequately controlled.

Basal TEWL

Basal or baseline TEWL refers to the resting rate of evaporative water loss through normal, non-perturbed skin.

Basal TEWL is generally low in healthy, intact skin, although significant differences can occur between different anatomical sites.

It is used as an important endpoint when studying natural variation in skin barrier function across factors such as age, body site and other individual characteristics.

TEWL in Cosmetic Research

Evaluating Skin Barrier Products

TEWL can be used to evaluate whether a cosmetic product supports or affects the skin barrier. Changes in TEWL before and after product application can provide objective information about changes in evaporative water loss.

Assessing Moisturising Formulations

Moisturising and barrier-supporting formulations can be evaluated using TEWL alongside other measurements of skin hydration and skin condition.

A reduction in TEWL may indicate improved resistance to evaporative water loss, although TEWL should be interpreted together with other relevant parameters rather than used as the sole measure of product performance.

Measuring Skin Stress and Recovery

TEWL can also be used in cosmetic research to assess how the skin responds to controlled stress or irritation and how quickly barrier function returns towards baseline.

TEWL Measurement Instruments

Several non-invasive instruments are commonly used to measure TEWL.

Tewameter® Evaporimeter

The Tewameter® evaporimeter, manufactured by Courage + Khazaka in Cologne, Germany, is one of the established instruments used for measuring transepidermal water loss.

Dermalab TEWL Module

The Dermalab TEWL module, developed by Cortex Technologies in Hadsund, Denmark, is another system used for non-invasive TEWL measurements.

ServoMed® Evaporimeter

The ServoMed® evaporimeter, manufactured by Servomed in Varberg, Sweden, is also used for evaluating evaporative water loss from the skin.

TEWL and Skin Permeability

TEWL is primarily a measurement of evaporative water loss and skin barrier function. The relationship between TEWL and the skin's permeability to topical substances has been investigated extensively.

While some in vitro evidence has questioned whether TEWL can directly predict the permeability of skin to topical substances, subsequent validation studies have continued to support TEWL as an important objective measure of the skin barrier to evaporative water loss.

For cosmetic formulation and research, TEWL is therefore best understood as a specific measure of water loss and barrier function rather than a universal measurement of skin permeability.

Why Is TEWL Important in Cosmetic Formulation?

TEWL provides formulators and cosmetic researchers with an objective parameter for evaluating the condition of the skin barrier.

When developing moisturisers, barrier-supporting products and other skincare formulations, TEWL measurements can complement subjective assessments and other instrumental measurements. This can help provide a more complete picture of how a product influences skin hydration and barrier function.

References

Source: Dermatologic, Cosmeceutic and Cosmetic Development – Kenneth A. Walters, Michael S. Roberts.

What Are Age Spots?

Age spots, also known as liver spots or solar lentigines, are flat areas of increased pigmentation that commonly appear on parts of the skin that receive regular sun exposure.

They are most frequently seen on the face, backs of the hands, shoulders, arms and other exposed areas. Their colour can range from light brown to darker brown, and they can vary considerably in size and intensity.

Age spots become more common with increasing age, but their development is strongly associated with cumulative exposure to ultraviolet (UV) radiation rather than age alone.

What Causes Age Spots?

Sun Exposure

Long-term exposure to ultraviolet radiation is one of the main factors associated with the development of age spots. Repeated UV exposure can stimulate melanocytes, the pigment-producing cells in the skin, leading to localised increases in melanin production.

Over time, this can result in areas of pigmentation becoming more visible.

Skin Ageing

The natural ageing process can also influence the appearance of pigmentation. Changes in melanocyte activity and the skin's ability to regulate pigmentation can contribute to a more uneven skin tone.

Cumulative UV Damage

Age spots are generally associated with cumulative rather than isolated sun exposure. This means that pigmentation can become increasingly noticeable after years of repeated exposure, even when individual periods of sun exposure did not cause an immediately visible change.

Where Do Age Spots Commonly Appear?

Face

The face is one of the most common locations because it receives frequent exposure to sunlight throughout the year.

Hands

The backs of the hands can develop age spots because they are often exposed to UV radiation and are not always protected with sunscreen.

Shoulders and Arms

These areas can develop visible pigmentation following repeated sun exposure, particularly in people who spend significant time outdoors.

Other Sun-Exposed Areas

Age spots can occur on other areas of the body that receive cumulative UV exposure, including the upper chest and neck.

Cosmetic Approaches to Age Spots

Cosmetic products cannot change the underlying cause of established pigmentation, but appropriately formulated skincare can help improve the appearance of uneven skin tone over time.

Skin-Brightening Ingredients

Ingredients such as Vitamin C, niacinamide and certain botanical extracts are commonly used in cosmetic formulations targeting uneven pigmentation and dull-looking skin.

These ingredients can work through different mechanisms and are often combined in formulations designed to promote a more uniform-looking complexion.

Exfoliating Ingredients

Certain alpha hydroxy acids and other exfoliating ingredients can help remove accumulated dead skin cells from the surface of the skin. Regular exfoliation can contribute to a smoother and more even-looking complexion.

The concentration and formulation need to be appropriate for the intended skin type and frequency of use.

Antioxidant Ingredients

Antioxidants can help protect the skin from oxidative stress associated with environmental exposure. Ingredients such as Ascorbic Acid (Vitamin C) are therefore frequently incorporated into cosmetic formulations designed to support brighter, healthier-looking skin.

Prevention of Age Spots

Sun Protection

Limiting UV exposure is one of the most important cosmetic and skincare considerations for preventing the appearance and worsening of sun-related pigmentation.

Broad-spectrum sunscreen, protective clothing and limiting prolonged direct sun exposure can help reduce cumulative UV exposure.

Consistent Skincare

A consistent skincare routine can help maintain an even-looking complexion. Depending on the individual's needs, this may include moisturising, antioxidant and skin-brightening products together with appropriate sun protection.

Age Spots and Cosmetic Product Development

Targeted Skincare

Age spots are an important target for the development of brightening and anti-ageing skincare products. Serums, creams, masks and targeted treatments can be formulated with combinations of ingredients selected to address uneven-looking skin tone.

Ingredient Selection

When developing a product targeting age spots, ingredient selection should consider the desired mechanism of action, formulation compatibility, stability, skin tolerance and applicable cosmetic regulations.

Managing Cosmetic Claims

Cosmetic products should be positioned around improving the appearance of pigmentation rather than making medical claims about diagnosing, treating or curing pigmentation disorders.

It is also important to distinguish common age spots from other types of pigmented lesions. A new, changing or unusual pigmented lesion should be assessed by a qualified healthcare professional rather than treated solely as a cosmetic concern.

References

Source: Dermatologic, Cosmeceutic and Cosmetic development - Kenneth A. Walters, Michael S. Roberts

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What Is Accelerated Stability Testing?

Accelerated stability testing is a method used to evaluate the stability of a cosmetic product by exposing it to controlled conditions that can accelerate potential changes in the formulation.

The approach is particularly useful in cosmetic product development because development cycles are often relatively short. Waiting for a product to undergo its entire intended shelf life under normal storage conditions may not be practical during the initial development process.

Accelerated testing can therefore provide earlier indications of how a formulation is likely to behave over time and can help identify potential stability problems before a product is launched.

Why Is Accelerated Stability Testing Used?

Supporting Faster Product Development

Cosmetic products often need to move from concept to market within a relatively short development cycle. Accelerated stability testing can provide useful information within a shorter period than conventional long-term stability studies.

This allows potential formulation or packaging problems to be identified earlier in the development process.

Predicting Stability

The results obtained under accelerated conditions can provide an indication of how a formulation may behave during storage. They can help formulators assess whether the product is likely to maintain its intended physical, chemical and aesthetic characteristics over time.

Accelerated testing should, however, be interpreted carefully. Results obtained under stress conditions are used to support stability predictions rather than simply being treated as a direct replacement for real-time stability monitoring.

Identifying Formulation Problems

Accelerated conditions can help reveal changes that may otherwise take considerably longer to become apparent.

These changes may include alterations in appearance, colour, odour, viscosity, pH, phase stability or other characteristics relevant to the particular formulation.

Supporting Formulation Optimisation

The information obtained during accelerated testing can also be used to improve the formulation. If a prototype shows instability under the selected conditions, the formulation can be modified and tested again before moving further into the development process.

Conditions Used in Accelerated Stability Testing

The exact conditions used depend on the type of cosmetic product and the purpose of the study. Different environmental factors can be used to stress the formulation.

Elevated Temperature

Increased temperature is commonly used to accelerate physical and chemical changes within a formulation. This can help identify temperature-sensitive ingredients, phase instability or other changes that may affect product quality.

Temperature Cycling

Repeated changes between different temperature conditions can be used to assess how a formulation responds to temperature fluctuations.

This can be particularly relevant for products that may experience changing temperatures during transportation or storage.

Light Exposure

Light can affect certain cosmetic ingredients, colours and fragrances. Where relevant, controlled light exposure can be included in a stability program to evaluate the product's sensitivity to light.

Other Environmental Conditions

Depending on the formulation and packaging, other environmental factors may also need to be considered. The accelerated stability program should therefore be adapted to the specific characteristics and intended use of the product.

What Is Evaluated During Accelerated Stability Testing?

Physical Properties

The physical characteristics of the formulation can be monitored throughout the study. Depending on the product, this can include appearance, colour, odour, texture, viscosity, pH and phase separation.

Chemical Stability

Where relevant, chemical testing can be used to determine whether key ingredients remain stable or whether degradation occurs under the selected conditions.

Microbiological Quality

For products where microbiological stability is relevant, microbiological testing can also form part of the overall stability program.

The preservation system and the formulation as a whole should be considered when evaluating microbiological stability.

Accelerated Stability Testing and Different Formulations

Emulsions

Creams and lotions can be particularly sensitive to temperature and other environmental stresses. Accelerated testing can help identify changes such as separation, changes in viscosity or other signs of physical instability.

Serums and Gels

Serums and gels can be monitored for changes in viscosity, clarity, colour, pH and the stability of relevant active ingredients.

Anhydrous Formulations

Oil-based and other anhydrous products may require particular attention to oxidation, changes in odour, colour and texture.

Cleansing Products

Shampoos, shower gels and other surfactant-based formulations can be evaluated for changes in viscosity, appearance, odour, colour, pH and other relevant properties.

Accelerated Stability Testing and Packaging

Formula-Packaging Compatibility

The packaging can have a significant influence on product stability. Accelerated testing can therefore be performed using the intended packaging system rather than only laboratory containers.

Potential interactions between the formulation and packaging materials should be considered during development.

Protection from Environmental Factors

Packaging can influence the product's exposure to oxygen, light, moisture and temperature. Appropriate packaging can therefore contribute to maintaining the stability of the formulation throughout its intended life.

Accelerated Testing and Real-Time Stability

Accelerated stability testing provides valuable information during development, but it should not automatically be considered a complete substitute for monitoring a product under normal storage conditions.

A commonly accepted approach is to support predictions obtained through accelerated testing with post-launch monitoring of retained samples stored under ambient conditions. The information obtained from this ongoing monitoring can also help improve future formulations and refine the accelerated stability methodology.

This approach is particularly useful because accelerated conditions can reveal potential problems quickly, while real-time monitoring provides information about how the finished product actually behaves under normal storage conditions.

Accelerated Stability Testing in Cosmetic Product Development

Accelerated stability testing is therefore best viewed as part of a broader stability strategy rather than as a standalone test.

A suitable stability program should be adapted to the individual product, considering its formulation, packaging, intended storage conditions and expected shelf life. The results can then be used together with real-time monitoring and other relevant testing to support formulation development and product quality.

For cosmetic manufacturers, this approach can help identify instability earlier, reduce unnecessary development time and improve confidence in the formulation before commercial launch.

References

Source: Guidelines on Stability Testing of Cosmetic Products – COLIPA.

What Is Cosmetic Stability Testing?

Stability testing is the process of evaluating whether a cosmetic product maintains its intended quality, safety, functionality and aesthetic characteristics throughout its expected shelf life.

The purpose of stability testing is to determine how a formulation behaves over time when exposed to different environmental conditions. Testing can identify changes that may affect the product's appearance, texture, colour, odour, chemical composition, microbiological quality or overall performance.

Stability testing is particularly important when developing a new cosmetic product or modifying an existing formulation, as even relatively small changes to the formula, manufacturing process or packaging can influence long-term stability.

Why Is Stability Testing Important?

Maintaining Product Quality

A cosmetic product should continue to meet its intended quality specifications throughout its expected period of use. Stability testing helps identify whether properties such as appearance, colour, texture, viscosity, pH and odour remain within acceptable limits over time.

Supporting Product Safety

Changes in a formulation can potentially affect its microbiological quality or the stability of individual ingredients. Stability testing helps identify potential problems before a product reaches the market.

Determining Shelf Life

The results of stability testing contribute to determining how long a cosmetic product can be expected to remain within its specified quality parameters under appropriate storage conditions.

Evaluating Formulation Performance

Stability testing can also reveal whether a formulation remains functional over time. For example, an emulsion may separate, a product may change viscosity, or an active ingredient may degrade.

Types of Stability Testing

The specific stability program depends on the type of cosmetic product, its formulation, packaging and intended market. A stability study may include several different types of testing.

Physical Stability Testing

Physical stability testing evaluates changes in the observable and measurable physical characteristics of a product.

Typical parameters can include appearance, colour, odour, texture, viscosity, pH and phase separation. For emulsions, for example, stability testing can help identify signs of creaming, flocculation, coalescence or complete separation.

Chemical Stability Testing

Chemical stability testing evaluates whether the chemical composition of the formulation remains within the required specifications over time.

This can include monitoring the concentration or degradation of relevant ingredients and identifying changes that could affect product performance or quality.

Microbiological Stability Testing

Microbiological testing evaluates whether the product remains within appropriate microbiological quality limits during storage.

This is particularly important for formulations containing water or other components that may support microbial growth. The preservation system and the formulation as a whole need to be considered when evaluating microbiological stability.

Stability Testing Conditions

Cosmetic products can be exposed to different environmental conditions during storage, transportation and use. Stability programs therefore commonly evaluate products under controlled conditions that can accelerate or reveal potential changes.

Temperature

Temperature can significantly affect the physical and chemical stability of a cosmetic formulation. Products may therefore be exposed to different temperatures to evaluate their behaviour under both normal and stress conditions.

Humidity

Humidity can be relevant to certain formulations and packaging systems, particularly where moisture exposure can influence the product or its packaging.

Light Exposure

Light can contribute to the degradation of certain ingredients, fragrances or colourants. Light exposure may therefore be considered when evaluating products that contain light-sensitive components.

Freeze-Thaw Conditions

Products may also be exposed to repeated freezing and thawing cycles. This can be particularly useful for evaluating emulsions and other formulations that may be sensitive to temperature fluctuations during transportation or storage.

Stability Testing for Different Cosmetic Products

Emulsions

Creams, lotions and other emulsions require particular attention to physical stability. Testing can help determine whether the oil and water phases remain properly dispersed and whether changes in viscosity, appearance or texture occur over time.

Serums and Gel Formulations

Serums and gels can be evaluated for changes in viscosity, clarity, colour, pH and active ingredient stability, depending on the formulation.

Anhydrous Products

Oil-based and other anhydrous formulations may have different stability considerations, including oxidation, changes in odour, colour and texture, and the stability of sensitive ingredients.

Cleansing Products

Shampoos, shower gels and other surfactant-based products can be evaluated for changes in viscosity, appearance, colour, odour, pH and microbiological quality.

Stability Testing and Packaging

Formula and Packaging Compatibility

The stability of a cosmetic product is not determined by the formulation alone. The packaging can also influence the product's long-term performance.

Interactions between the formulation and packaging materials can potentially affect the product's appearance, composition or functionality. Packaging compatibility should therefore be considered as part of the stability development process.

Packaging Protection

Packaging can also protect a formulation from external factors such as light, oxygen and moisture. The choice of container, closure and dispensing system can therefore contribute to the overall stability of the finished product.

Designing a Stability Testing Program

Because cosmetic products vary significantly in their formulations and intended uses, there is no single stability testing program that is appropriate for every product.

The testing program should be designed according to the characteristics of the formulation, the packaging, the intended storage conditions and the expected product life. A reasonable and efficient stability program should provide sufficient information to identify relevant changes without making the development process unnecessarily disproportionate.

The original A&T Formulation content references the Guidelines on Stability Testing of Cosmetic Products published by COLIPA, which similarly emphasise that manufacturers should design stability programs appropriate to their individual products and activities.

Stability Testing and Shelf Life

Stability testing results are used together with other relevant product information to support decisions regarding the expected shelf life and appropriate storage conditions of a cosmetic product.

The objective is to establish that the product continues to meet its defined quality specifications for the period in which it is expected to remain on the market and in use.

Stability testing is therefore an important part of cosmetic product development rather than simply a final quality-control step. It can also help identify formulation or packaging problems early enough to allow the product to be improved before commercial production.

References

Source: Guidelines on Stability Testing of Cosmetic Products – COLIPA.

What Is a Cosmetic Product?

A cosmetic product is a substance or preparation intended to be placed in contact with external parts of the human body, including the skin, hair, nails, lips and external genital organs, or with the teeth and the mucous membranes of the oral cavity.

According to the European cosmetic product definition, the main purposes of a cosmetic product are to clean, perfume, change the appearance, correct body odours, protect or maintain the treated parts of the body in good condition.

This definition is important because it establishes both the intended areas of application and the functions that a product may perform while being classified as a cosmetic.

What Products Are Considered Cosmetics?

Cosmetic products cover a broad range of personal care categories. They can include products designed for the skin, hair, nails, lips, teeth and oral cavity.

Skincare Products

Examples include creams, emulsions, lotions, gels, oils, face masks, tinted bases and other products intended for application to the skin.

Haircare Products

Cosmetic hair products include shampoos, conditioners, hair oils, hair-setting products and products designed for colouring, waving, straightening or otherwise styling the hair.

Makeup and Colour Cosmetics

Makeup products such as foundations, powders, facial and eye makeup, lip products and other colour cosmetics can fall within the cosmetic product category.

Cleansing and Bath Products

Soaps, shower gels, bath foams, bath oils and other cleansing or bathing preparations can be considered cosmetic products when they meet the relevant definition and requirements.

Deodorants and Personal Hygiene Products

Deodorants, antiperspirants and products intended for external intimate hygiene can also fall within the cosmetic product category.

Oral Care Products

Products intended for the care of the teeth and mouth, including toothpastes and other oral hygiene preparations, may also be classified as cosmetics under the applicable European framework.

Nail Care Products

Nail care and nail makeup products, including nail polishes, are also included within the broad range of cosmetic products.

What Functions Can a Cosmetic Product Perform?

The intended function is an important part of determining whether a product falls within the cosmetic product definition.

Cleansing

Cosmetic products can be intended to clean the skin, hair, teeth or other permitted areas of application.

Perfuming

Products such as perfumes, eau de Cologne and other fragranced preparations can be used primarily to impart or enhance a pleasant scent.

Changing Appearance

Makeup, hair colourants and other cosmetic products can be designed to alter or enhance the appearance of the treated area.

Protecting and Maintaining

Cosmetic products can also be formulated to protect the skin or other permitted areas of application and to help maintain them in good condition.

Correcting Body Odour

Deodorants and related personal care products can be designed to reduce or correct undesirable body odours.

Cosmetic Products Under EU Regulation

The definition of a cosmetic product in Europe is supported by the requirements established under Regulation (EC) No 1223/2009 on cosmetic products.

The Regulation provides the principal legal framework governing cosmetic products placed on the EU market. It covers areas including product safety, responsible persons, product information, ingredients, labelling and other requirements that need to be fulfilled before a cosmetic product is marketed.

For cosmetic product development, understanding the regulatory classification of the product is therefore an important part of the development process.

Products That Can Be More Difficult to Classify

Some products can have characteristics that make their classification less straightforward, particularly when their intended function overlaps with another regulatory category.

Sun Protection Products

Suntanning and sun-related preparations can fall within the cosmetic category in Europe when they meet the applicable definition and requirements. Their regulatory treatment can differ between markets.

Antiperspirants

Antiperspirants can also be considered cosmetic products within the European framework, although their classification and regulatory treatment may differ in other parts of the world.

Anti-Dandruff Products

Anti-dandruff shampoos are another example where classification can depend on the product's intended function and the regulatory framework of the market in which the product is sold.

This highlights the importance of assessing not only the ingredients in a product but also its intended purpose, claims and presentation.

Cosmetic Products and Product Development

Product Concept

The intended purpose of a cosmetic product should be established at the beginning of development. This helps determine the appropriate formulation approach, target application area and regulatory requirements.

Formulation

The formulation needs to be developed around the intended cosmetic function while taking into account ingredient compatibility, stability, safety and sensory properties.

Claims

The claims used to describe a cosmetic product should be consistent with its intended cosmetic function and supported by appropriate evidence where required.

Regulatory Compliance

Before placing a cosmetic product on the EU market, the formulation and finished product need to meet the applicable requirements of the EU Cosmetics Regulation. Regulatory considerations should therefore be integrated into product development rather than addressed only at the end of the process.

Cosmetic Products in Different Markets

Although the EU provides a clear regulatory framework for cosmetic products, the classification of certain products can vary between countries and regions.

A product that is considered a cosmetic in Europe may be regulated differently in another market depending on its ingredients, intended use, claims and presentation.

For brands planning international distribution, regulatory assessment should therefore be carried out for each intended market.

References

Source: Safety Assessment of Cosmetics in Europe – Vera Rogiers and Marleen Pauwels.

Source: Regulation (EC) No 1223/2009 of the European Parliament and of the Council on cosmetic products.