How Is Cosmetic Product Efficacy Demonstrated? Understanding Scientific Efficacy Testing

How Is Cosmetic Product Efficacy Demonstrated? Understanding Scientific Efficacy Testing

Subtitle: How are claims about skin hydration, elasticity, and appearance scientifically evaluated? What is the difference between laboratory research and human studies?

We often encounter cosmetic products that claim to hydrate the skin, improve elasticity, or reduce the appearance of fine lines. But how can we determine whether these effects actually occur?

Does a biological change observed in a laboratory mean that the same effect will occur in human skin? Is feeling that your skin is more hydrated the same as measuring an increase in skin hydration using scientific instruments?

Modern cosmetic science addresses these questions through various research methods. This process is known as cosmetic efficacy evaluation and, more broadly, claim substantiation.

The same scientific principles apply when investigating plants with a long history of traditional use, such as Rosa damascena, and the cosmetic products derived from them.

In this article, we explore how cosmetic efficacy testing works, how research findings should be interpreted, and what scientific evidence can—and cannot—demonstrate.

1. How Do We Know Whether a Cosmetic Product Is Effective?

Three fundamental concepts must be distinguished when scientifically evaluating cosmetic products: quality, safety, and efficacy.

Quality assessment examines whether a product meets established physical, chemical, and microbiological specifications.

Safety assessment investigates the potential risks a product may pose to human health under its intended and reasonably foreseeable conditions of use.

Efficacy evaluation examines whether a product delivers its claimed cosmetic benefits and what evidence supports those claims.

For example, a rose water product that meets microbiological requirements and passes stability testing may have undergone important quality and safety evaluations. However, these results alone do not demonstrate that the product increases skin hydration or reduces the appearance of fine lines.

Those effects may require separate studies designed to evaluate the relevant parameters.

Why Do Cosmetic Claims Require Scientific Evidence?

European Commission Regulation (EU) No 655/2013 establishes common criteria for cosmetic product claims, requiring explicit and implicit claims to be supported by adequate and verifiable evidence.

The supporting evidence should be relevant to the claim, and the research methods should be scientifically valid, reliable, and reproducible.

In Canada, Section 21 of the Cosmetic Regulations also establishes evidence requirements for certain claims relating to the effects of cosmetics or their ingredients on the chemistry of the skin, hair, or teeth, as well as specified safety claims.

The underlying scientific principle is straightforward:

First, define the effect being investigated. Then, select a scientific method capable of evaluating that effect.

Not every cosmetic product needs to undergo the same tests. The type and extent of evidence required depend on the product's characteristics and the nature of the claims being made.

2. How Is Cosmetic Efficacy Investigated in the Laboratory?

One approach commonly used in cosmetic research is in vitro testing.

The term in vitro refers to studies conducted outside a living organism under controlled laboratory conditions.

Researchers may use cell cultures and other suitable biological models to investigate how a cosmetic product or ingredient interacts with specific cellular processes.

Some of the parameters examined in these studies include:

• Cell viability: Evaluating how a tested material affects cell survival and viability.

• Cell proliferation: Investigating changes associated with cell growth and multiplication.

• Oxidative stress markers: Examining biological responses associated with cellular oxidative processes.

• Melanin production: Assessing changes related to pigmentation mechanisms.

• Collagen- and elastin-related biomarkers: Investigating biological processes associated with skin structure.

Another approach, known as ex vivo testing, involves studying tissues or biological materials obtained from living organisms under controlled experimental conditions.

These methods are valuable for understanding potential mechanisms of action and comparing formulations during product development.

What Can Laboratory Findings Actually Demonstrate?

A change in a collagen-related biomarker observed in a cell culture does not directly prove that the same product reduces wrinkles in human skin.

Similarly, a laboratory finding involving melanin production is not equivalent to clinical evidence that a product reduces visible dark spots in people.

This distinction matters because laboratory models differ substantially from human skin.

Factors such as skin penetration, application frequency, ingredient concentration, and the biological characteristics of the skin can all influence the outcome.

In vitro studies help researchers understand biological mechanisms, but they do not directly measure a product's cosmetic performance on human skin.

3. How Are Changes in Human Skin Measured?

Studies involving human volunteers may be conducted to evaluate how cosmetic products perform under actual conditions of use.

In addition to professional assessments, researchers can use specialized scientific instruments to measure the skin's physical properties.

The measurement method is selected according to the cosmetic effect being investigated.

How Is Skin Hydration Measured?

Instruments such as the Corneometer® assess hydration in the outermost layer of the skin by measuring electrical properties associated with its water content.

In a typical study, baseline measurements are recorded before the product is applied.

The product is then used according to a predefined protocol, and measurements are repeated at appropriate intervals.

Changes in skin hydration can be evaluated by comparing the baseline and subsequent measurements.

Why Is TEWL Important?

Transepidermal Water Loss (TEWL) refers to the movement of water through the skin into the surrounding environment.

TEWL measurements are widely used as one of the indicators for evaluating skin barrier function.

However, skin hydration and TEWL are not the same parameter.

A product that improves measured skin hydration does not necessarily produce a corresponding change in TEWL.

Likewise, a change in TEWL alone should not automatically be interpreted as proof that the skin barrier has been repaired.

How Are Skin Elasticity and Wrinkles Evaluated?

Instruments such as the Cutometer® apply controlled suction to the skin to assess deformation and recovery characteristics.

For studies involving the appearance of fine lines and wrinkles, researchers may use three-dimensional skin imaging, profilometry, and standardized photographic analysis.

These techniques can help quantify changes in skin surface characteristics using parameters appropriate to the study.

Colorimetric systems used in skin tone research also allow changes in skin colour to be assessed objectively.

The reliability of these measurements depends not only on the instruments used, but also on the study protocol, measurement conditions, and appropriate interpretation of the results.

4. Professional Assessments and Consumer Experiences: What Is the Difference?

Scientific instruments are not the only tools used to evaluate cosmetic products.

Dermatologists and other appropriately qualified professionals may assess changes in skin appearance using predefined grading scales.

Such assessments can examine dryness, flaking, roughness, fine lines, and overall skin appearance.

Another approach is consumer use testing.

In these studies, participants use a product for a specified period and answer questions about their experience.

For example:

• Does your skin feel more hydrated?

• Do you think your skin feels softer?

• Are you satisfied with the product?

The important point is to understand precisely what the results represent.

Consider the following hypothetical example:

"87% of participants reported that their skin felt softer."

This statement describes participants' subjective experiences.

By contrast:

"The product increased skin softness by 87%."

The second statement describes a quantified change and requires a different type of supporting evidence.

Consumer experiences provide valuable information about how cosmetic products are perceived and used.

However, subjective experiences and objective measurements cannot be treated as interchangeable forms of evidence.

This distinction is particularly important when presenting customer testimonials in scientifically responsible product communications.

5. What Makes a Cosmetic Efficacy Study Scientifically Reliable?

The fact that a cosmetic product has been scientifically tested does not automatically mean that every claim made about it has been demonstrated.

The reliability of a study depends on its overall design, not simply on the testing method or instrument used.

What Should Be Considered in Study Design?

Participant selection: Volunteers should be appropriate for the research objectives in terms of age, skin type, and the characteristics being investigated.

Sample size: The number of participants should be sufficient to evaluate the effect under investigation with an appropriate degree of reliability.

Duration of use: Some hydration effects can be assessed through short-term measurements, whereas certain changes in skin appearance may require longer periods of product use.

Controls and comparisons: Depending on the study objectives, researchers may use untreated control areas, control groups, reference products, or other appropriate comparison methods.

Measurement conditions: Environmental factors such as temperature, relative humidity, and skin preparation should be controlled, particularly in studies measuring skin hydration.

Statistical analysis: The magnitude of the observed changes, variability, confidence intervals, and statistical significance should be evaluated together.

What Does Statistical Significance Mean?

A statistically significant result does not necessarily mean that the observed change is large enough to be noticeable in everyday life.

A small difference may be statistically significant without representing a meaningful cosmetic improvement for the consumer.

For this reason, findings should be evaluated in terms of both their statistical properties and their cosmetic relevance.

Is "Clinically Tested" Enough?

The phrase "clinically tested" does not, by itself, explain how effective a product is.

To understand the scientific value of a study, several questions should be considered:

1. Which product or ingredient was tested?

2. What method was used?

3. How many people participated, or which laboratory model was used?

4. Which parameter was measured?

5. What did the results actually demonstrate?

Another important distinction is the difference between research on an individual ingredient and testing of a finished cosmetic product.

For example, findings from a study involving a Rosa damascena extract cannot automatically be applied to rose water produced using a different process or to a cream containing rose-derived ingredients.

Production methods, chemical composition, concentration, formulation, and conditions of use may all influence the results.

Scientific evidence must always be interpreted in relation to the specific material investigated and the claim being made.

6. Rosa damascena and Rose Distillate Research: The Akita Example

Rosa damascena is an important botanical species that has attracted scientific interest because of its aromatic characteristics and long history of traditional use.

However, not all products derived from rose flowers have the same chemical composition.

Rose essential oil, rose distillate, and rose extracts produced using different solvents vary in their manufacturing processes and constituent profiles.

Consequently, a biological effect observed in a particular rose extract cannot automatically be assumed to occur in pure rose distillate.

How Is Akita Non-Deoiled Rose Water Evaluated?

Akita Non-Deoiled Rose Water is a rose distillate developed through a distillation process in which the rose oil is not separately removed as a distinct product.

The single-ingredient product is identified by the INCI name Rosa Damascena Flower Distillate.

Laboratory evaluations conducted on Akita's Non-Deoiled Rose Water provide a practical example of how cosmetic research findings should be interpreted.

These evaluations have explored research parameters associated with skin hydration, signs of skin ageing, pigmentation, and cellular processes.

However, the meaning of each finding must be determined according to the test model and the specific parameter measured.

For example, a laboratory observation involving cell proliferation does not, on its own, prove that a product accelerates skin renewal in humans.

Similarly, a change in a pigmentation-related biological marker is not equivalent to clinical evidence that a product reduces visible dark spots on human skin.

Laboratory findings should therefore be clearly distinguished from cosmetic effects demonstrated through appropriately designed human studies.

Is an Eye Irritation Test the Same as Evidence of Benefits for the Eyes?

Among the evaluations conducted on samples of Akita's pure Non-Deoiled Rose Water is an eye irritation assessment based on the OECD Test Guideline 491 method.

OECD 491 is an in vitro testing method used in the hazard classification of chemicals with respect to eye damage and irritation.

Results obtained using this method provide information about the irritation-related hazard classification of the tested sample under the specified laboratory conditions.

However, such findings do not, by themselves, demonstrate that the product:

• Relieves dry eye symptoms.

• Treats eye diseases.

• Is safe for direct instillation into the eyes.

Investigating a potential benefit for dry eye symptoms would require separate clinical research specifically designed for that purpose.

Furthermore, a test result obtained for a particular Akita product sample cannot automatically be generalized to other rose water products with different formulations or manufacturing processes.

How Should Scientific Evidence Be Classified?

When communicating research involving Rosa damascena and rose-derived cosmetic products, four types of evidence should be distinguished.

Each type of evidence provides valuable information.

However, because they address different scientific questions, they do not carry the same meaning or support the same conclusions.

7. How Should Consumers Interpret Scientific Claims About Cosmetics?

When a cosmetic product refers to scientific research on its label, packaging, or promotional materials, the most important question is not simply whether testing was performed.

It is equally important to understand what the research demonstrated and the limits within which its conclusions are valid.

The fact that a plant used in a cosmetic formulation has been scientifically studied does not mean that every claimed benefit of the finished product has been demonstrated.

Similarly, a product that has undergone safety assessment has not necessarily demonstrated all its claims relating to hydration, elasticity, or pigmentation.

A scientifically well-supported claim should have a clear relationship with the method used and the results obtained.

Responsible scientific communication makes this relationship understandable without drawing conclusions that extend beyond the available evidence.

Conclusion from Rose Academy

The traditional use of plants provides a valuable foundation for modern cosmetic research. However, traditional knowledge and scientifically demonstrated cosmetic efficacy are not the same.

Laboratory studies help researchers investigate biological mechanisms. Human studies can evaluate product performance under defined conditions of use. Safety assessments examine potential risks, while consumer studies explore users' experiences and perceptions.

These distinctions are equally important when interpreting research involving Rosa damascena and the rose distillates derived from it.

The scientific value of a cosmetic product is not determined solely by the number of tests performed, but also by the questions those tests address and how accurately their results are interpreted.

Three principles form the foundation of credible cosmetic science:

The right claim. The right testing method. The right interpretation.

References

1. European Commission. (2013). Commission Regulation (EU) No 655/2013 laying down common criteria for the justification of claims used in relation to cosmetic products.EUR-Lex

2. Cosmetics Europe. (2019). Guidelines for Cosmetic Product Claim Substantiation.Cosmetics Europe

3. Cosmetics Europe. (2008). Guidelines for the Evaluation of the Efficacy of Cosmetic Products, Revised Version.Cosmetics Europe

4. OECD. (2025). Test No. 491: Short Time Exposure In Vitro Test Method for Identifying Chemicals Inducing Serious Eye Damage and Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage. OECD Guidelines for the Testing of Chemicals. DOI: 10.1787/9789264242432-en

5. Government of Canada. Cosmetic Regulations, Section 21: Claims.Justice Laws Website

Scientific Note: This article is intended to explain the scientific methods used to evaluate cosmetic efficacy. Research examples involving Akita products are discussed within the scope of the relevant testing methods. Laboratory findings should not be interpreted as clinically demonstrated therapeutic effects or as proof of efficacy in humans unless supported by appropriate clinical evidence.