Broad-spectrum sunscreens containing the TriAsorB™ filter: In vitro photoprotection and clinical evaluation of blue light-induced skin pigmentation

Background: Blue light (BL), particularly high-energy visible (HEV) light (400-450 nm), can cause skin damage and pigmentation. Therefore, effective sunscreens should offer photoprotection beyond ultraviolet (UV) radiation to also prevent or limit BL-induced cutaneous effects. Objectives: To evaluate the in vitro BL photostability and photoprotection properties of nine sunscreens containing the broad-spectrum UV/BL phenylene bis-diphenyltriazine (PBDT or TriAsorB (TM)) filter, together with three other organic UV filters, and to assess the in vivo photoprotection level provided by two of these products against BL-induced skin pigmentation. Methods: In vitro BL photostability and photoprotection factors, comprising the percentage of BL radiation stopped by the product (%BL) and the critical wavelength extended to BL (BL-CW), were determined by spectrophotometry. The in vivo photoprotection provided by two representative sunscreens (i.e. similar formulations, one non-tinted and one tinted) was assessed in two open randomized studies (20 and 16 women, respectively) after exposure of two test areas (with and without sunscreen) on the back of each subject to a 412-nm irradiation dose at 50 J/cm(2), using instrumental and clinical measurements of skin pigmentation. The percentage sunscreen photoprotective effectiveness (%PPE) was calculated by comparing intrasubject post-exposure pigmentation changes between the with and without sunscreen test areas. Results: In vitro, the nine PBDT-containing products were highly photostable and had a BL-CW >= 385 nm and a %BL >= 30% (range: 30%-50%), thus allowing effective BL photoprotection. In vivo, both representative sunscreens prevented BL-induced immediate skin pigmentation (1 and 24 h post-exposure) with %PPE values ranging from 50.7% to 75.5% for colorimetric assessments (p < 0.001) and from 31.2% to 72.7% for visual scores (p <= 0.001). Conclusions: All PBDT-containing sunscreens were considered effective at absorbing BL radiation in vitro. The two representative broad-spectrum sunscreens tested in subjects significantly reduced BL-induced immediate skin pigmentation following single exposure to monochromatic BL radiation.