Screening and evaluation of sunscreen cosmetics for sensitive facial skin / 中华皮肤科杂志

ABSTRACT

Objective:To screen and evaluate sunscreen cosmetics for sensitive facial skin.Methods:From June to August in 2019, 40 subjects with positive lactic acid sting test were recruited from the staff of Chongqing Traditional Chinese Medicine Hospital, and subjected to human skin closed patch testing with 4 kinds of sunscreen cosmetics for sensitive skin (marked as products Ⅰ, Ⅱ, Ⅲ, Ⅳ respectively) separately. Then, the 40 subjects were equally divided into 2 groups to apply 2 sunscreen products with relatively higher safety (according to the above closed patch testing results) on the face respectively. Erythema, edema and desquamation were evaluated at baseline, 2 and 4 weeks after application of the 2 products, and non-invasive measurement methods were used to detect transepidermal water loss (TEWL) , stratum corneum hydration, skin melanin content and skin sebum content. In additon, the 2 products were applied on the back of the subjects separately, and an ultraviolet solar simulator was used to determine the sun protection factor (SPF, n = 12) and protection factor of UVA (PFA, n = 11) . Measurement data were compared using paired t test and one-way analysis of variance, and nonparametric data were compared using Wilcoxon signed rank test. Results:Patch testing showed that only 1 subject developed a grade 1 reaction to the sunscreen product Ⅲ, no subjects showed positive reactions to the product Ⅳ, and the safety of products Ⅲ and Ⅳ was higher than that of the other 2 products. Subjective safety evaluation revealed that the degree of erythema after 4-week application of products Ⅲ and Ⅳ was significantly lower than that before application (Wilcoxon signed rank test, Z = 4.73, 4.82 respectively, both P < 0.05) . Objective efficacy evaluation revealed that the TEWL, stratum corneum hydration and skin melanin content significantly differed among different time points (baseline, after 2- and 4-week application of products Ⅲ and Ⅳ, all P < 0.05); after 4-week application of products Ⅲ and Ⅳ, the TEWL (30.05 ± 1.47, 30.37 ± 1.28 respectively) and skin melanin content (112.58 ± 7.34, 103.47 ± 5.48 respectively) were significantly lower than those before application (all P < 0.05) , and the stratum corneum hydration (62.35 ± 2.67, 63.72 ± 2.54 respectively) was significantly higher than that before application (both P < 0.05) . At week 4, the skin melanin content was significantly lower in the product Ⅳ group (103.47 ± 5.48) than in the product Ⅲ group (112.58 ± 7.34, t = 8.45, P < 0.05) . The SPF and PFA values of the product Ⅳ (51.8 ± 2.9, 10.1 ± 1.2 respectively) were both significantly higher than those of the product Ⅲ (31.5 ± 2.6, 7.4 ± 0.7, t = 15.34, 24.66, respectively, both P < 0.05) . Conclusion:Comprehensive application of closed patch testing, long-term application test and sun protection index determination can be used to screen and evaluate the safety and efficacy of sunscreen cosmetics for sensitive facial skin.