A randomized double-blind two-sequence two-period crossover clinical trial in healthy adults with sensitive skin comparing a metabolite-based soap with a neutral control soap to evaluate effects on skin hydration, skin barrier function, sensitive skin burden, microbiome composition, lipid profile, and cellular energy markers
Sensitive skin
Participants are enrolled in a randomized, double-blind, two-sequence, two-period crossover clinical trial comparing a metabolite-based soap (test product) with a neutral control soap. Participants are randomly assigned in a 1:1 ratio to one of two treatment sequences. Block randomisation is used to allocate participants to each group: Sequence AB: metabolite soap followed by control soap Sequence BA: control soap followed by metabolite soap Each treatment period lasts 4 weeks, separated by a 3-week washout period using a neutral cleanser. A 2-week washout phase using the neutral cleanser is performed before baseline. Participants wash the face and volar forearm twice daily with the assigned soap during each treatment period. The metabolite-based soap contains a blend of postbiotic metabolites derived from fermentation of lactic acid bacteria. The control soap has an identical base formulation but does not contain the metabolite complex. Clinical and mechanistic assessments are performed at baseline and at the end of each treatment period and include measurements of skin hydration, transepidermal water loss, sensitive skin questionnaire scores, microbiome analysis, and biochemical markers. Compliance is monitored through participant diaries and product weight verification.
1. Healthy male or female adults aged 20–45 years 2. Fitzpatrick skin types II–V 3. Self-reported sensitive skin with BoSS ≥“mild” at screening 4. Stable skincare and lifestyle habits for ≥4 weeks prior to enrollment 5. Agreement to avoid use of any other facial or forearm cleansers, topical actives, or cosmetics during the study 6. Willingness to provide written informed consent
1. Presence of chronic skin disorders (eczema, psoriasis, dermatitis) 2. Use of systemic or topical antibiotics, corticosteroids, or retinoids within 8 weeks before baseline 3. Cosmetic procedures (peeling, laser, microneedling) within 3 months 4. Known allergy or hypersensitivity to soap ingredients 5. Pregnancy or breastfeeding 6. Participation in another clinical study within the preceding 3 months