How Can You Know If a Cosmetic Formula Is Really Good Enough?
A client often asks us a very reasonable question:
“How do I know that the formula you developed for us is actually suitable, safe and compliant?”
It is a more complicated question than it first appears.
A formula can look excellent in the laboratory and feel exactly right during application. But that alone does not prove that it is stable, microbiologically safe, compatible with its packaging, suitable for long-term use, or properly supported from a regulatory perspective.
At A&T Formulation, we look at this question from three different angles:
- Does the product work for the intended user?
- Can its quality and safety be supported by appropriate testing?
- Has the finished cosmetic product been professionally assessed from a regulatory and safety perspective?
Only when these three areas come together can we have real confidence in the result.
A Good Formula Is More Than a Good Laboratory Sample
The first mistake is to think that successful product development ends when the client approves a laboratory sample.
It does not.
A laboratory sample is a development tool. It allows the formulator and client to evaluate the concept, make adjustments and gradually establish the desired product.
The client may assess the cream's texture, absorption, fragrance, appearance and overall experience. A smaller user group may also test the product and provide feedback.
That feedback is valuable because some aspects of a cosmetic product simply cannot be reduced to a laboratory number.
A cream can have an appropriate viscosity and still feel too heavy.
A cleanser can have excellent cleansing properties and still leave an unpleasant after-feel.
A serum can have an elegant appearance but dispense poorly from its packaging.
This is why product development is inherently iterative.
1. The User Has to Like the Product
The first level of validation is therefore the user experience.
During development, samples can be provided for evaluation and feedback. Based on this feedback, the formulation can be adjusted until the product reaches the intended target.
The questions may be very practical:
- Does the product spread easily?
- Does it absorb as expected?
- Does the skin feel comfortable afterwards?
- Is the fragrance appropriate?
- Is the texture consistent with the intended positioning?
- Does the product deliver the experience the client wants?
This type of evaluation is not a replacement for laboratory testing.
It answers a different question.
The Handbook of Cosmetic Science and Technology discusses consumer and sensory testing as an important component of cosmetic claim support and explains that some claims, particularly those involving consumer acceptance or sensory perception, can require consumer studies.
In other words, the consumer experience is part of product performance.
Why User Feedback Alone Is Not Enough
Imagine that twenty people test a new moisturiser and all of them like it.
That is useful information.
But it does not tell us whether the emulsion will remain stable during storage.
It does not tell us whether the preservative system can control microbial growth when challenged.
It does not establish whether the finished product is compatible with its packaging.
And it does not constitute a complete regulatory safety assessment.
This is why cosmetic product development needs several layers of evidence.
The second layer comes from testing.
2. What Do Laboratory Tests Actually Tell Us?
Different tests answer different questions.
There is no single laboratory test that proves a cosmetic product is “good”.
Instead, a testing strategy is built around the characteristics and intended use of the product.
Some of the most important areas include stability and compatibility, microbiological quality, preservation efficacy and, where relevant, specific efficacy or safety testing.
The Handbook of Cosmetic Science and Technology describes stability testing as an important tool during formulation development because it can identify formulation and packaging-related problems before they reach the consumer.
This is particularly important because cosmetic products change over time.
The question is not whether a product will remain absolutely unchanged forever.
It is whether the changes that occur remain within acceptable limits for the intended product.
Stability and Compatibility: Does the Product Remain Suitable?
Stability testing examines how a cosmetic formulation behaves over time under defined conditions.
Depending on the product, relevant parameters can include:
- appearance;
- colour;
- odour;
- pH;
- viscosity;
- phase separation;
- other physical characteristics;
- and, where relevant, the behaviour of the active or delivery system.
Compatibility testing adds another important dimension:
Does the formulation remain suitable when it is in contact with its final packaging?
A formula can be stable in a laboratory container but interact differently with the actual packaging.
For example, packaging can influence the product through contact with its materials, closure system, air exposure or dispensing mechanism.
The stability literature specifically highlights formulation/package-related problems and describes stability testing as an early-warning system that can help identify potential issues before a product reaches consumers.
At A&T, stability and compatibility are therefore considered throughout development and are subsequently evaluated using the intended packaging and defined testing conditions.
The exact protocol depends on the product, packaging and intended shelf life.
Challenge Testing: Can the Preservation System Do Its Job?
For many water-containing cosmetic products, preservation is a critical part of formulation development.
A product does not leave the factory and then remain untouched.
Consumers open it, dispense it, touch it and expose it to their environment.
This creates opportunities for microorganisms to enter the product during normal use.
A preservative efficacy test, commonly referred to as a Challenge Test, evaluates whether the preservation system is capable of controlling deliberately introduced microorganisms under the defined test conditions.
The Cosmetic Microbiology: A Practical Approach literature explains that preservation is not limited to adding a preservative to the finished formula. Microbiological control involves raw materials, manufacturing intermediates, finished products and the conditions under which the product is used.
This is an important distinction.
The question is not simply:
“Does this formula contain a preservative?”
The more meaningful question is:
“Does the complete preservation system provide adequate microbiological protection for this particular formulation?”
The exact testing requirement depends on the product and applicable regulatory framework, so it should not be reduced to the simplistic rule that every product containing water is automatically subject to exactly the same test protocol.
Microbiological Testing: Was the Product Manufactured Properly?
Challenge testing and microbiological purity testing are related, but they are not the same thing.
A microbiological purity test examines the microbiological quality of the finished product.
It can include assessment of total microbial counts and the absence of specified microorganisms, depending on the applicable method and product.
This tells us something about the microbiological condition of the batch that was actually manufactured.
That distinction matters.
A formula can have an effective preservation system and still become contaminated during manufacturing if production hygiene or process control is inadequate.
The cosmetic microbiology literature therefore emphasises microbiological control throughout manufacturing rather than treating preservation as something that begins only after production is complete.
For this reason, microbiological testing is an important part of confirming the quality of the finished batch.
3. What If We Want to Make a Claim About the Product?
There is another question that frequently gets overlooked:
What are we actually promising the consumer?
Suppose a brand wants to say that a cream:
- increases skin hydration;
- reduces the appearance of wrinkles;
- improves skin firmness;
- is suitable for sensitive skin;
- provides long-lasting moisturisation;
- or produces a measurable improvement in skin appearance.
The formula itself does not automatically prove these statements.
The claim needs appropriate substantiation.
The Handbook of Cosmetic Science and Technology describes several possible approaches, including literature evidence, in vitro testing, instrumental measurements, expert evaluation, clinical studies and consumer testing. It also emphasises that the appropriate method depends on the type of claim being made.
This is a crucial principle:
The claim should determine the evidence strategy.
You do not begin by choosing a test simply because it is available.
You first define what you want to claim.
Then you determine what evidence can reasonably support that claim.
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Instrumental Testing vs. Clinical Testing vs. Consumer Testing
These approaches are complementary rather than interchangeable.
Instrumental testing
Instrumental methods provide objective measurements.
Depending on the product and claim, these can include measurements related to hydration, skin elasticity, pigmentation, skin surface properties or other parameters.
They are particularly useful when the claim can be connected to a measurable physical characteristic.
Clinical or in vivo testing
In vivo testing evaluates the product directly on human volunteers.
The Handbook of Cosmetic Science and Technology describes human clinical studies as one of the most direct ways to demonstrate a product effect, with assessment potentially involving expert evaluation, biometric measurement or subjective user assessment.
Consumer testing
Consumer studies are particularly relevant when the claim concerns perception or user experience.
For example, “easy to spread” is fundamentally different from a claim such as “increases skin hydration”.
One is primarily perceptual.
The other can be supported by objective measurement.
This is why simply asking consumers whether they like a product cannot replace instrumental or clinical evidence where those forms of evidence are needed.
And Then Comes the Professional Safety Assessment
The third layer is perhaps the one clients are least able to evaluate themselves.
A product may perform well in testing and still require a professional assessment of its safety and regulatory status.
The Cosmetic Product Safety Report (CPSR) and associated regulatory documentation are part of the framework used to establish that the cosmetic product can be placed on the market in accordance with the applicable requirements.
The safety assessment is not simply a document confirming that the product “passed a test”.
It involves evaluating available information about the ingredients and finished product and determining whether the product is safe for its intended use.
The Handbook of Cosmetic Science and Technology describes safety assessment as a structured process in which existing information is gathered and evaluated, with additional testing considered where the available information is insufficient.
This is why the role of the safety assessor is fundamentally different from that of the formulator.
The formulator develops the product.
The laboratory generates relevant evidence.
The safety assessor evaluates the available safety information and performs the professional safety assessment.
So, How Do We Know the Formula Is Appropriate?
At A&T, we would describe it as a three-layer validation process.
1. User validation
The client and, where appropriate, selected users evaluate the product.
This helps establish whether the formulation delivers the intended sensory and practical experience.
2. Independent testing
Appropriate laboratories and testing procedures provide objective information about characteristics such as:
- stability;
- packaging compatibility;
- microbiological quality;
- preservation efficacy;
- skin compatibility;
- and specific product efficacy or claims.
Not every product needs every possible test. The testing strategy should be appropriate to the product and the claims being made.
3. Professional regulatory and safety review
The final product documentation is reviewed by the appropriate qualified professional, including the safety assessment required for the applicable market.
This provides a separate level of professional oversight.
And that separation is valuable.
Why the Three Layers Matter Together
Consider a new facial cream.
The client likes the texture and fragrance.
That is good.
The stability study shows that the emulsion remains physically acceptable over the defined conditions.
That is good too.
Microbiological testing confirms that the finished batch meets the relevant microbiological criteria.
The preservation system has also been appropriately evaluated.
Then, if the brand wants to claim a measurable improvement in skin hydration, an appropriate efficacy study can provide evidence for that specific claim.
Finally, the finished product information is assessed as part of the regulatory and safety documentation.
Now we have something much stronger than a formula that simply “looks good”.
We have different types of evidence answering different questions.
The A&T Perspective: Product Development Is a Process of Verification
This is how we approach product development at A&T Formulation.
We do not see the laboratory sample as proof that the final commercial product is ready.
The laboratory phase establishes the formulation.
Scale-up demonstrates that it can be reproduced under manufacturing conditions.
Stability and compatibility testing examine whether the product and packaging remain suitable.
Microbiological testing evaluates the finished batch.
Challenge testing helps assess preservation efficacy where applicable.
Additional dermatological, instrumental, clinical or consumer testing can be selected according to the product objectives and claims.
And professional safety and regulatory assessment provides the final layer of oversight.
Each stage answers a different question.
That is exactly why they work together.
The Bottom Line
When a client asks, “How can I know that my cosmetic formula is really suitable?”, there is no single test that provides the entire answer.
Confidence comes from several independent pieces of evidence.
The user tells us whether the product delivers the intended experience.
Laboratory testing tells us whether the formulation meets defined physical, microbiological, stability and, where required, efficacy or compatibility criteria.
The qualified safety and regulatory professional evaluates the available information and determines whether the finished product can satisfy the applicable safety and regulatory requirements.
This separation is important because cosmetic product quality is multidimensional.
A product needs to be more than pleasant to use.
It needs to be well formulated, reproducible, stable, appropriately tested, properly documented and safe for its intended use.
That is what turns a laboratory formula into a professionally developed cosmetic product.
References
- Barel, A. O., Paye, M., & Maibach, H. I. (Eds.). (2009). Handbook of Cosmetic Science and Technology, 3rd ed. Informa Healthcare. Chapters covering stability testing, cosmetic claims substantiation, in vitro and in vivo testing, expert evaluation and consumer testing.
- Gehring, W., & Gehlsen, U. (2006). Cosmetic Microbiology: A Practical Approach. Taylor & Francis. Chapters covering preservation strategies, microbiological quality and contamination during manufacturing and consumer use.
- Benson, H. A. E., Roberts, M. S., Leite-Silva, V. R., & Walters, K. A. (Eds.). (2019). Cosmetic Formulation: Principles and Practice. CRC Press. Material covering sensory analysis, claims substantiation and the selection of appropriate testing approaches for cosmetic claims.
- Rosen, M. R. (Ed.). (2005). Delivery System Handbook for Personal Care and Cosmetic Products: Technology, Applications, and Formulations. William Andrew Publishing. Chapter on clinical testing and emerging testing technologies for personal care products, including safety and claims substantiation.
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