Sensitive skin is a fully-fledged evaluation territory in cosmetics. Its declared prevalence reaches 50 to 60% of the female population in Western countries, and the claims targeting it — tolerance, comfort, redness reduction, barrier strengthening — are among the most sought after by brands. But evaluating a product on sensitive skin requires specific CRO expertise: rigorous panel selection, adapted protocols, measurement equipment combining objective and subjective parameters. This guide details the criteria for selecting the right laboratory partner for this type of study.
What is sensitive skin? Definition and subtypes
Sensitive skin is not a homogeneous clinical entity. It is defined as a syndrome characterized by unpleasant sensations — tingling, burning, itching, tightness — in response to stimuli that do not normally provoke these sensations in people with normal skin. These sensations can be triggered by cosmetic, environmental, dietary, or emotional factors.
At the pathophysiological level, several mechanisms are involved:
Barrier dysfunction: elevated TEWL and reduced stratum corneum hydration facilitate irritant penetration and lower the threshold of skin reactivity. This mechanism is particularly documented in atopic dermatitis and rosacea.
Neurosensory hyperreactivity: increased activation of TRPV1 (Transient Receptor Potential Vanilloid 1) and TRPA1 receptors in cutaneous nerve fibers amplifies the perception of stimuli. This mechanism explains subjective sensations without visible inflammatory signs.
Cutaneous microbiome dysbiosis: alterations in microbiome composition (reduction in protective Staphylococcus epidermidis, proliferation of Staphylococcus aureus) are documented in sensitive and atopic skin, contributing to low-grade inflammation.
| Subtype | Dominant mechanism | Clinical signs | Target population |
|---|---|---|---|
| Functional sensitive skin | Barrier dysfunction + neurosensory | Transient redness, tingling | Women 25–45 years |
| Reactive skin | Vascular hyperreactivity | Flushing, diffuse erythema | Fair phototypes |
| Mild atopic skin | Barrier deficit + Th2 inflammation | Xerosis, pruritus, mild eczema | All ages |
| Rosacea | Neurovascular inflammation | Persistent redness, telangiectasia | Women 30–50 years |
| Sensitive male skin | Post-shave irritation + barrier dysfunction | Tightness, burning | Adult men |
Panel selection criteria for sensitive skin
The quality of the subject panel is the primary validity factor in a sensitive skin study. A serious CRO must be able to document its inclusion and exclusion criteria, and present panel qualification data.
Validated inclusion criteria
Two approaches are commonly used to qualify sensitive skin:
Standardized self-declaration: the Berardesca questionnaire or the Misery questionnaire, internationally validated, allow scoring of declared skin sensitivity. A score above a defined threshold qualifies the subject as sensitive skin. This approach is simple but subjective.
Lactic Acid Sting Test (LAST): application of a 10% lactic acid solution to the nasolabial fold. Subjects presenting stinging rated ≥ 2 on a 0 to 3 scale at 3 and 5 minutes are qualified as sensitive skin. This test objectifies neurosensory reactivity and is considered one of the reference markers of sensitive skin.
Methyl nicotinate flush test (MN Flush Test): application of a methyl nicotinate solution inducing dose-dependent vasodilation. Laser Doppler measurement of blood flow allows quantification of vascular reactivity and selection of hyperreactive subjects.
Mandatory exclusion criteria
- Systemic or local corticosteroid treatment in the 4 weeks prior to the study
- Active skin pathology in flare (eczema, psoriasis, severe rosacea) on the study area
- History of cosmetic contact allergy (positive patch test)
- Pregnancy or breastfeeding
- Significant sun or artificial UV exposure in the 4 weeks prior to the study
Evaluation methods specific to sensitive skin
Objective parameters: barrier and inflammation
The biometrological methods used for normal skin apply to sensitive skin, with reference values specific to this population:
TEWL: sensitive skin generally presents a higher baseline TEWL than normal skin, reflecting the underlying barrier dysfunction. The reduction in TEWL after treatment constitutes the primary functional proof for barrier strengthening claims on sensitive skin.
Erythema and blood flow: the Mexameter® (erythema index) and Laser Doppler Flowmetry quantify vascular reactivity and low-grade inflammation, particularly relevant for redness reduction claims.
Stratum corneum hydration: the Corneometer® measures baseline hydration, generally lower on sensitive skin, and the response to treatment.
Skin microbiome: for formulas positioned on the microbiome-barrier link, 16S-qPCR analyses on skin samples (swabs) allow evaluation of changes in microbiome composition, particularly the Staphylococcus epidermidis / Staphylococcus aureus balance.
Subjective and neurosensory parameters
Subjective evaluation is inseparable from sensitive skin studies. It relies on validated and standardized tools:
Sensation scales: subjects score the intensity of their sensations (tingling, burning, itching, tightness) on visual analogue scales (VAS) or numerical rating scales (NRS 0–10) at defined time points after application. These data are processed statistically and constitute primary or secondary endpoints depending on the claim.
Quality of life questionnaires: the DLQI (Dermatology Life Quality Index) or the SKINDEX-29 allow evaluation of the impact of the skin condition on quality of life and its change under treatment.
Hedonic sensory evaluation: texture, spreadability, immediate and 4-hour comfort, absence of discomfort — these data are collected by standardized questionnaire and complement the objective evaluation.
| Parameter | Method | Type | What it demonstrates |
|---|---|---|---|
| TEWL | Tewameter, Aquaflux | Objective | Barrier dysfunction, treatment response |
| Erythema | Mexameter, Colorimeter | Objective | Inflammation, redness |
| Blood flow | Laser Doppler | Objective | Vascular reactivity |
| SC hydration | Corneometer | Objective | Dryness, hydrating response |
| Microbiome | 16S-qPCR, swabs | Objective | Cutaneous microbial balance |
| Sensations | VAS, NRS | Subjective | Comfort, perceived tolerance |
| Quality of life | DLQI, SKINDEX | Subjective | Global daily impact |
| Reactivity (LAST) | Lactic acid | Functional | Panel qualification, hyperreactivity |
Standard protocols by target claim
“Tested on sensitive skin — demonstrated tolerance”
Panel of 30 to 50 subjects with qualified sensitive skin (positive LAST or validated self-declaration). Product applied as intended for 28 days. Clinical dermatologist evaluation at D0, D14, D28. TEWL, Corneometer, Mexameter at D0 and D28. Sensation questionnaire at D0, D7, D14, D28. No adverse reaction required to validate tolerance.
“Reduces redness” or “soothes sensitive skin”
Panel of 40 to 60 subjects with sensitive skin and declared redness. TEWL, Mexameter, Laser Doppler at D0, D14, D28. Sensation questionnaire at each visit. Erythema scoring by dermatologist. The claim is substantiated by a statistically significant decrease in erythema index and sensation scores.
“Strengthens the barrier of sensitive skin”
Panel of 30 to 40 subjects with sensitive skin and confirmed elevated baseline TEWL. TEWL and Corneometer at D0, D14, D28 (±D56). Optional tape stripping for ceramide or lipid formulas, with biochemical analysis of strips. The claim is substantiated by a significant reduction in TEWL and improvement in stratum corneum hydration.
“Rebalances the microbiome of sensitive skin”
Panel of 30 subjects with sensitive skin and qualified microbiome at inclusion. Skin swab sampling at D0 and D28. 16S-qPCR analysis with quantification of key species (S. epidermidis, S. aureus, diversity ratio). Combined with TEWL and sensation questionnaire to link the microbiome effect to the clinical barrier effect.
What an expert sensitive skin CRO must be able to provide
When selecting a CRO for a sensitive skin study, the elements to request are:
Panel database: the CRO must have a database of qualified sensitive skin subjects, with the results of their LAST or qualification questionnaire. A database of several hundred qualified subjects is an indicator of experience in this field.
Documented qualification protocols: the CRO must present its sensitive skin qualification method, the tools used (LAST, questionnaires), and the cutoff criteria applied.
Neurosensory expertise: the collection and statistical processing of subjective data (VAS, NRS, questionnaires) requires specific expertise. The CRO must be able to present previous studies with subjective endpoints.
Multiparametric capacity: TEWL, Mexameter, Corneometer, Laser Doppler, clinical dermatologist evaluation, and neurosensory evaluation must all be available within the same establishment to avoid biases linked to inter-site subject travel.
On the Skinobs platform, brands can identify laboratories specialized in sensitive skin testing, filter by evaluation method and geographic area, among the 138 referenced laboratories in 38 countries.
Conclusion
Evaluating a product on sensitive skin is an exercise in precision. It requires a carefully qualified panel, protocols combining objective and subjective measurements, and a CRO experienced in managing this particular population. The rigor of partner selection directly conditions the solidity of the claims file — and the confidence the brand can place in the results obtained.
Looking for a specialized laboratory to evaluate your formula on sensitive skin? Skinobs allows you to identify expert CROs and protocols adapted to your claims. [Access the platform]
