Study on screening and evaluation methods of cosmetics for people with facial sensitive skin

OBJECTIVE: The purpose of this study is to screen and evaluate cosmetic products for sensitive skin on the face. METHODS: Thirty-five subjects with positive lactic acid sting test (LAST) were recruited from the staff of our hospital from November 2019 to February 2020. First, the human skin enclosed patch test of cosmetic gel (abbreviated as gel) was performed, and then the tested products were continuously applied for 4 weeks to complete the long-term efficacy test. Subjects’ sensation of application, pruritus, tingling and burning were assessed on a 0 to 9 scale prior to, 14, and 28 days after topical application. Moreover, the transepidermal water loss rate (TEWL), stratum corneum (SC) hydration, melanin index (MI), erythema index (EI) and dendritic cells and inflammatory cell infiltration were noninvasively detected by the tester. LAST were performed before applying, 14 and 28 days after application, and then the test results were compared. RESULTS: In this study, a total of 34 people participated in the test. The results of human skin enclosed patch test indicated that only 1 case of grade 1 reaction occurred among the tested subjects. The subjects felt good after applying the products, and the gel showed high degree of skin comfortable, no irritation and good tolerability. Subjective safety evaluation illustrated that the scores of pruritus, tingling and burning of the subjects decreased in D14 and D28 patient revisit, showing statistically significant differences (P < .05). When the gel was applied for 4 weeks, TEWL (8.42 ± 1.12) and EI (201.35 ± 13.51) were lower than the results before application (P < .05), and the SC hydration (65.36 ± 2.56) was higher than that before application (P < .05). There was no correlation between the SC hydration and TEWL (R = 0.092, P = .416). The results of skin CT indicated that the number of facial dendritic cells decreased in 17 subjects (accounting for 50%) in D28 patient revisit, and the degree of inflammatory cell infiltration decreased in 27 subjects (accounting for 80%). Compared with the baseline value, the LAST score and total sensory score decreased after application the product for 4 weeks, and the difference was statistically significant (the mean value of P < .05). CONCLUSION: The subjective feeling of application and efficacy of cosmetics in people with sensitive skin could be successfully evaluated by the comprehensive application of human skin enclosed patch test, long-term trial test, subjective safety evaluation and objective efficacy evaluation. And it provides the basis to judge whether the cosmetic is consistent with the efficacy claim of sensitive skin.