Cosmetic Efficacy Studies: Understanding, Choosing, and Valuing Scientific Evidence

In a cosmetic market where innovation is constant and competition fierce, proving a product's real efficacy has become an essential credibility criterion — both for professionals and consumers. Far from being a simple marketing formality, cosmetic efficacy studies follow strict methodologies designed to objectify the benefits of skincare products on skin, hair, or nails. They are at the heart of scientific validation of cosmetic claims, governed by European regulations (Regulation EC No. 1223/2009) and European Commission recommendations.

Why conduct cosmetic efficacy studies?

The main objective of an efficacy study is to scientifically demonstrate that a product delivers on its promises: hydration, anti-aging, radiance, regeneration, soothing, sebum regulation, etc. These studies validate product claims written on packaging, marketing materials, and technical sheets. In the European Union, any claim must be based on verifiable, sincere, and relevant evidence, in accordance with Regulation (EU) No. 655/2013.

Beyond regulatory aspects, these studies play a strategic role in product development:

• They guide formulation choices.
• They reassure distributors and healthcare professionals.
• They strengthen consumer confidence, notably through measurable figures and before/after visuals.

What types of efficacy studies exist?

There are three main families of efficacy studies, which can be combined according to product type, positioning, and claimed effects.

1. Instrumental studies (objective)

These studies use standardized measuring devices, operated by specialized laboratories, to quantify biological or physical skin modifications. They provide objective, quantified, and reproducible results.

Among the most common:

• Corneometry: measures skin hydration levels.
• Cutometry: evaluates skin elasticity and firmness.
• Tewametry (TEWL): measures transepidermal water loss, thus barrier function.
• Chromametry: measures color variations (radiance, redness, spots).
• 3D Profilometry: evaluates wrinkles and skin relief.
• Sebometry: quantifies sebum secretion.
• Standardized before/after photography with digital image analysis.

These tests are performed in vivo on volunteer panels, often double-blind with comparators (placebo or untreated product), over variable durations (7 to 56 days or more).

2. Clinical tests under dermatological supervision

These are conducted on human volunteers according to a protocol supervised by a physician (dermatologist or investigating physician). This type of study allows observation of the product's global effects under real-use conditions but with scientific supervision.

The investigator evaluates:

• Skin condition (touch, suppleness, desquamation, redness).
• Evolution of visible signs (fine lines, dryness, comedones...).
• Any adverse effects or skin reactions.

These tests are often associated with satisfaction questionnaires completed by volunteers, allowing collection of "sensory-subjective" data.

3. Consumer use tests (self-evaluation)

These studies involve having the product tested by a targeted consumer panel (by skin type, age, specific needs), at home or in simulated conditions. Participants complete a standardized questionnaire after a usage period (often 21 to 28 days). Their sensory perceptions (texture, fragrance, comfort), impressions of perceived efficacy, and purchase intent are collected. Although subjective, these tests are valuable for understanding product acceptability, user experience, and coherence between marketing promise and actual experience.

How are efficacy studies regulated?

Efficacy studies must meet legal criteria for cosmetic claims (truthfulness, sincerity, sufficient data, relevance, loyalty, informed consumer decision). These principles are defined by regulation (EU) No. 655/2013 and detailed in the European Commission's Technical Guidelines (Annex III of the 2017 document).

In practice, this involves:

• Selection of an independent laboratory or evaluation center.
• Drafting a precise protocol validated before study.
• Rigorous statistical analysis of results (significance, effect size).
• Conservation of complete reports in the PIF (Product Information File) as claim evidence.