In vitro comparison – A new accessible and reliable statistical method to compare the global UV protection properties of cosmetics
The comparison of products regarding their properties for sun protection is till now just possible with re measuring their indices. But this concept can lead to misinterpreted and besides by single checking with SPF value. There is no very comparative method for checking different cosmetics – supposed similar but with possible different performance for example – include different physical-chemistry checking (UV filters concentration, particle and/or droplet size, viscosities, etc.). This article describes a new statistical interpretation for sunscreen product comparison by three stepped checking based on all absorbance spectrum by means of an in vitro method.
Claims of sun protection performance for a cosmetic product must be demonstrate but the most reliable manner to express it is still in debate. Choice of kind of endpoint, UV spectrum range, etc. These are examples of questions which are treated all over the world such as in ISO committee. For these purposes, several relevant standards has been published for in vivo and in vitro methods (1, 2, 3). Being able to express a level of protection with the most relevant methods is indeed important but being able to ensure the control of the remaining of these properties is quite of interest unless still badly considered. Clearly properties of a product will change during ageing, producing several batches, during development with little modification of formula, etc. As there are several endpoints - SPF (Sun Protection Factor), UVA-PF, Critical Wavelength, etc.- a single checking is not possible to guarantee the equivalence. Nevertheless, SPF evaluation is commonly use for this purpose but it is really inappropriate because we never know how to appreciate the differences between two SPF values. Two products may have the same SPF value without being id ...