Phototoxic assessment of a sunscreen formulation and its excipients: An in vivo and in vitro study

Abstract

Background: Cosmetic preservatives are used to protect cosmetic formulations and improve its shelf-life. However, these substances may exert phototoxic effects when used under sunlight.

Objective: To assess safety, efficacy and putative phototoxic effects of a sunscreen formulation SPF 30 and its excipients.

Materials/methods: Irradiation was performed with solar simulated light (SSL) and the sunscreen from the School of Pharmacy/UFRJ/Brazil. We used albino hairless mice in different groups (control (G1), only irradiated (G2), sunscreen plus irradiation (G3) and vehicle plus irradiation (G4) for morphological assessment and immunefluorescence detection to OKL38. In vitro analyses were with a Saccharomyces cerevisiae (SC) strain plus SSL in the presence of methylparaben, propylparaben, imidazolidinyl urea, aminomethyl propanol and their association.

Results: G3 and G4 displayed photosensitization leading to thickening of the epidermis and increased dermal cellularity. G4 displayed strong OKL38 labeling when compared with other groups. Aminomethyl propanol, methylparaben and propylparaben are endowed with phototoxic activity against SC. Propylparaben displayed the highest phototoxic effect, followed by excipients association.

Conclusions: The sunscreen's vehicle is endowed with phototoxic activity. Propylparaben was the most phototoxic agent, increasing the overall phototoxicity of excipient association, pointing to a critical concern regarding vehicle associations intended to cosmetic purposes.

Keywords: Aminomethyl propanol; Methylparaben; Propylparaben; Simulated solar light and Saccharomyces cerevisiae.