Multidimensional Evaluation of a Dual-Compartment Sheet Mask for Skin Whitening and Repair of UV-Induced Erythema and Pigmentation: Human Efficacy Assessment and In Vitro Evidence

Skin hyperpigmentation and ultraviolet (UV)-induced photodamage represent prevalent cosmetic concerns that demand safe and effective topical intervention strategies. This study evaluated the skin-whitening, pigmentation-improving, and post-UV repair efficacy of a novel dual-compartment sheet mask (DCSM) formulated with eight complementary depigmenting ingredients, namely niacinamide, α-arbutin, glabridin, hexylresorcinol, ascorbyl tetraisopalmitate (VC-IP), paeonol, Camellia japonica flower extract and Ormosia henryi bark extract, through two independent human efficacy studies and in vitro cell experiments. In a 28-day, self-controlled human efficacy study (Cohort 1; n = 32), regular DCSM use was associated with significant increases in the individual typology angle (ITA), significant decreases in the b* value, significant reductions in H-channel standard deviation (H-SD), significant decreases in the melanin index (MI), and significant diminishment of pigment spot area and optical density, suggesting progressive and sustained improvements in skin tone, uniformity, and pigmentation. In a separate UV-induced skin erythema model (Cohort 2; n = 30), seven days of daily DCSM application significantly attenuated UV-induced increases in MI, erythema index (EI), and a* value while promoting recovery of skin lightness (ITA) relative to untreated control sites, indicating effective post-sun erythema alleviation and pigmentation suppression. In vitro, treatment of α-MSH-stimulated A-875 human melanoma cells with 5% (v/v) DCSM emulsion significantly suppressed intracellular melanin synthesis at a non-cytotoxic concentration, providing supportive evidence consistent with the human efficacy findings observed in vivo. Collectively, these multidimensional findings indicate that DCSM use was associated with improvements in skin hyperpigmentation, an even skin tone, and facilitated recovery from UV-induced photodamage, supporting its potential as a cosmetic intervention for pigmentation regulation and post-sun skin repair.