Fatty Acids in Cosmetics: Functions, Benefits and Vegetable Oils

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.

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.