Sunscreen efficacy against UVA1- and visible light- induced skin pigmentation is influenced by ethnicity

BackgroundThere is growing evidence that individuals with different skin phototypes require tailored approaches to achieve optimal photoprotection. Individuals with darker skin phototypes are more prone to UVA1- and visible light-induced pigmentation, whereas lighter phototypes are more susceptible to shorter wavelengths such as UVB and UVA2. Thus, skin phototype is an important determinant of sunscreen efficacy. In the present study we have asked if ethnicity - independent of phototype - is another factor affecting sunscreen efficacy. Objectives(i) To determine the overall photoprotective effects of two sunscreen formulations against UVA1, visible light (VL), and combined visible light plus UVA1, and (ii) to compare the photoprotective efficacy of both products between Han Chinese and Caucasian participants. MethodsForty healthy volunteers (N=20 Han Chinese; N=20 Caucasian), matched for phototype, constitutive pigmentation, gender, and age, were exposed to VL, UVA1, and combined VL plus UVA1 to induce pigmentation responses following standardized irradiation protocols. Skin responses across treated and untreated sites were analysed using linear mixed-effects models. ResultsAcross all participants, both sunscreen formulations provided significant protection against VL, UVA1, and combined VL plus UVA1. Notably, photoprotective efficacy against UVA1-induced immediate (IPD) and persistent pigment darkening (PPD) differed significantly between ethnic groups, with one formulation showing stronger protection in Han Chinese. ConclusionThis study indicates that ethnicity could influence sunscreen efficacy. Thus, sunscreens should not only be tailored to different phototypes, but also consider ethnic background.