and standardizing a test procedure for UVA protection labelling.
Recently COLIPA has published the guidelines for in vitro UVA protection determination [4]. A sunscreen in vitro test is based on absorbance (calculated from transmittance) or reflectance measurements. It requires the definition of both the instrumentation to be used and the measurement procedure including substrate selection and relative application criteria of the sunscreens. With regard to the instrumentation, the absorption spectrum is the most relevant parameter for defining the protective performance of a sunscreen