Absence of human skin irritation and allergenic potential after repeated patch applications of a lamellar moisturizer

BACKGROUND: New cosmetic products should undergo clinical evaluation for skin sensitization potential. OBJECTIVES: To assess the irritation and sensitization potential of a moisturizer containing lamellar structured lipids after repeated patch application in humans, using human repeated insult patch test methodology. METHODS: This 6‐week, single‐center, open‐label study compared a lamellar moisturizer with negative saline control in human subjects aged 18‐70 years and skin phototype (Fitzpatrick) classification I–IV. During an initial induction phase, semi‐occlusive multi‐test patches were applied to the skin of participants’ backs three times per week for 3 consecutive weeks; clinical assessments were performed per International Contact Dermatitis Research Group criteria. Participants subsequently underwent a challenge phase, where a new patch was applied to a contact‐naïve area of the skin to assess sensitization to the moisturizer. RESULTS: The study commenced with 233 voluntary participants, 214 of whom completed the study and underwent the final dermatological assessment. Most participants (232/233; 99.6%) demonstrated negative patch test results. One participant had a positive reaction at the lamellar moisturizer application site, with visible erythema and edema (classified as an adverse event [AE]); however, this reaction was observed 24 hours after a reaction to another product in the patch test panel (a prototype cleanser). Importantly, no skin reactions were detected during the challenge phase. Two participants had AEs of mild contact dermatitis in the area of patch adhesive application during the induction phase. No serious AEs occurred during the study. CONCLUSIONS: These findings suggest that the lamellar moisturizer has low irritant and allergenic potential.