Natural photoprotection under scrutiny: an in vitro evaluation

Consumer interest in "natural" cosmetics has expanded to photoprotective products. Plant-derived ingredients, including oils and extracts, are frequently marketed as natural alternatives to conventional UV filters, often with claims of high photoprotective efficacy. However, their actual ability to provide broad-spectrum, clinically relevant photoprotection remains largely unverified, raising concerns about potential inadequate UV protection. In this study, eleven plant oils and nine cosmetic products marketed as "natural" (declared sun protection factor (SPF) 25-50) were tested. Test products were applied in standardized amounts on polymethyl methacrylate (PMMA) plates. Absorbance spectra were measured using an SPF Analyzer, then in vitro photoprotective parameters were calculated. Plant oils, including raspberry seed, carrot seed, coconut, shea butter, and others, exhibited negligible in vitro SPF and in vitro UVA PF values, with the exception of tamanu oil (in vitro SPF 21.5, in vitro UVA PF 3.3). However, its in vitro SPF decreased to 5.2 after photostability testing. Among cosmetic products, those containing primarily inorganic UV filters (titanium dioxide, zinc oxide) displayed variable efficacy, with most providing insufficient protection despite marketing claims, while one formulation containing titanium dioxide achieved high in vitro SPF (64.2) but low in vitro UVA PF (9.8). In overall, plant oils do not provide adequate photoprotection and cannot replace conventional UV filters. Consumers relying on such products may be unknowingly exposed to harmful UV radiation, potentially compromising dermatological interventions, including hyperpigmentation therapies. Effective photoprotection requires formulations containing multiple complementary UV filters, and highlights the need for standardized in vitro testing to ensure accurate product labelling and reliable consumer protection.