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™) 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/cm2 , 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.

Sub-optimal Application of a High SPF Sunscreen Prevents Epidermal DNA Damage in Vivo.

The cyclobutane pyrimidine dimer (CPD) is a potentially mutagenic DNA photolesion that is the basis of most skin cancers. There are no data on DNA protection by sunscreens under typical conditions of use. The study aim was to determine such protection, in phototypes I/II, with representative sunscreen-user application. A very high SPF formulation was applied at 0.75, 1.3 and 2.0 mg/cm2. Unprotected control skin was exposed to 4 standard erythema doses (SED) of solar simulated UVR, and sunscreen-treated sites to 30 SED. Holiday behaviour was also simulated by UVR exposure for 5 consecutive days. Control skin received 1 SED daily, and sunscreen-treated sites received 15 (all 3 application thicknesses) or 30 (2.0 mg/cm2) SED daily. CPD were assessed by quantitative HPLC-tandem mass spectrometry (HPLC-MS/MS) and semi-quantitative immunostaining. In comparison with unprotected control sites, sunscreen significantly (p ≤ 0.001-0.05) reduced DNA damage at 1.3 and 2.0 mg/cm2 in all cases. However, reduction with typical sunscreen use (0.75 mg/cm2) was non-significant, with the exception of HPLC-MS/MS data for the 5-day study (p <0.001). Overall, these results support sunscreen use as a strategy to reduce skin cancer, and demonstrate that public health messages must stress better sunscreen application to get maximal benefit.

Photoprotective effects of a broad-spectrum sunscreen in ultraviolet-induced cutaneous lupus erythematosus: a randomized, vehicle-controlled, double-blind study.

OBJECTIVE: We sought to assess if the exclusive use of a broad-spectrum sunscreen can prevent skin lesions in patients with different subtypes of cutaneous lupus erythematosus (CLE) induced by ultraviolet (UV) irradiation under standardized conditions. METHODS: A total of 25 patients with a medical history of photosensitive CLE were included in this monocentric, randomized, vehicle-controlled, double-blind, intraindividual study. The test product and its vehicle were applied 15 minutes before UVA and UVB irradiation of uninvolved skin areas on the upper aspect of the back in a random order, and standardized phototesting was performed daily for 3 consecutive days. RESULTS: Characteristic skin lesions were induced by UVA and UVB irradiation in 16 patients with CLE in the untreated area, and 14 patients showed a positive test result in the vehicle-treated area. In contrast, no eruptions compatible with CLE were observed in the sunscreen-treated area in any of the 25 patients. This resulted in significant differences (P < .001) between UV-irradiated sunscreen-treated versus vehicle-treated areas, and between UV-irradiated sunscreen-treated versus untreated areas. Furthermore, a significant difference (P < .05) was observed concerning the age of disease onset and the patient history of photosensitivity. Patients who were younger than 40 years at onset of CLE reported photosensitivity significantly more often than patients with a higher age of disease onset. None of the patients showed any adverse events from application of the test product or the vehicle. LIMITATIONS: Data resulting from standardized experimental phototesting might not be transferable to a clinical setting. CONCLUSION: These results indicate clearly that the use of a highly protective broad-spectrum sunscreen can prevent skin lesions in photosensitive patients with different subtypes of CLE.