Evaluation of the protection of sunscreen products against long wavelength ultraviolet A1 and visible light‐induced biological effects

Abstract

AbstractBackgroundLong wavelength ultraviolet‐A1 in combination with visible light induces hyperpigmentation, particularly in dark‐skin phototypes. This study evaluated the efficacy of four sunscreen formulations in protecting against VL + UVA1 (370–700 nm).MethodsThe test products (A–D) were applied to the back of 12 volunteers, then irradiated with 320 J/cm2 VL + UVA1 (3.5% UVA1 [370–400 nm]). Immediately after irradiation, and at Days 1, 7, and 14, erythema and pigmentation were assessed by investigator global assessment (IGA), colorimetry (Δa* and ΔITA) and diffuse reflectance spectroscopy (DRS)‐measured relative dyschromia (area under the curve AUC). Control areas were irradiated without sunscreen.ResultsProduct D, containing titanium dioxide 11%, iron oxides 1%, and antioxidants, provided the highest and most consistent protection. Compared with unprotected irradiated control, it had statistically significantly less erythema on IGA, DRS (Δoxyhemoglobin), and colorimetry (Δa*) at Day 0; less pigmentation on IGA at all time points, on DRS (relative dyschromia) at Days 7 and 14, and on colorimetry (ΔITA) at Day 0. Product B, containing zinc oxide 12% plus organic UV filters, iron oxides 4%, and antioxidants, also showed some efficacy.ConclusionOf the sunscreens tested, the tinted products provided better protection against VL + UVA1 than the non‐tinted products. Since the product with 1% iron oxides was superior to the product with 4% iron oxides, further studies are needed to evaluate whether iron oxide content correlates with better protection.