Change of ultraviolet absorbance of sunscreens by exposure to solar-simulated radiation.
Synopsis The photoprotective efficacy of some topical sunscreens was determined ex-vivo by spectrophotometric assay using an irradiation monochromator and a diffuse reflectance sphere. Transmission scans were run from 400 to 290 nm through human epidermis samples before and after application of products and protection factors (PF) were calculated. The results are also expressed as the percentage of the radiation stopped by the products in each spectral range (UVB, short UVA and long UVA). All the formulations contained two chemical filters: butyl methoxy dibenzoyl methane and octyl methoxycinnamate in a range of concentrations. Estimates of the effectiveness of all products were higher than results in humans when calculated by this ex-vivo technique. Due to its high discriminant power, this method constitutes a useful tool in the formulation of sunscreens.