Facial dermal exposure-related parameters and skincare behaviors among adult women from six cities in China

The face is a primary site of exposure to skincare products, cosmetics, and sunlight. However, population-specific data on facial dimensions and product use among adult women in China remain limited. Current dermal exposure assessments often rely on default parameters derived from European or North American populations, which may introduce uncertainty when applied to Chinese consumers. This study aimed to describe facial dermal exposure-related parameters and skincare behaviors among adult women in China and to explore their associations with sensitive skin status and objective skin biophysical measurements. This multicenter cross-sectional study included 5081 women aged 18–65 years from six Chinese cities, conducted between March 2025 and June 2025. Total and regional facial areas were measured using two-dimensional (2D) and three-dimensional (3D) imaging. Data on skincare practices, sun-protection behaviors, sociodemographic characteristics, and skin-related variables were collected using standardized questionnaires and objective skin biophysical measurements. Statistical analyses included descriptive statistics, Pearson correlation analysis, agreement analysis, between-group comparisons, cluster analysis, chi-square tests, and analysis of variance (ANOVA). The mean age of participants was 40.7 years, and the mean body mass index (BMI) was 23.4 kg/m 2 . The mean total 2D and 3D facial areas were 21,173.4 mm 2 (211.7 cm 2 ) and 39,381.0 mm 2 (393.8 cm 2 ), respectively; the 3D value (393.8 cm 2 ) was lower than the SCCS default facial application area of 565 cm 2 but close to the EPA-derived estimate of approximately 380 cm 2 . It should be noted that the proximity to the EPA-derived estimate does not constitute external validation of the measurement, as boundary definitions and measurement methods differ across sources. Valid 3D data were obtained from 4740 participants; 62.0% reported performing skincare twice daily. Total 2D and 3D facial areas were moderately correlated (r = 0.667, P < 0.001), while calibration, Bland–Altman, and ICC analyses demonstrated systematic differences and poor absolute agreement, indicating that measurements from the two systems were not interchangeable. Exploratory clustering suggested heterogeneous skincare behavior patterns, although cluster separation and stability were limited. This study provides system-generated facial-area estimates and descriptive data on skincare behaviors among adult women from a six-city convenience sample in China. The findings illustrate heterogeneity in facial-area measurements and skincare practices and may inform the development of localized dermal exposure scenarios. However, the facial-area estimates are device-specific and require independent validation, and the observed behavioral patterns and skin-related differences should be interpreted as exploratory cross-sectional associations rather than stable subgroups or causal relationships.