2008 British Journal of Dermatology
L'Oreal, Episkin, SkinEthic

Prediction of chemical absorption into and through the skin

Background formulations cannot be precisely evaluated.To date, risk assessment following topical exposure to cosmetic /dermatologicalObjectives skin and for risk assessment.To provide a tool for optimization of active permeation into /throughMethods of a chemical absorbed into and across the skin from a cosmetic formulation. Account was taken of (i) the ionization state of the chemical, tocorrect the skin A predictive model was developed for estimating the cumulative mass/dermatological/vehicle partition coefficient; and (ii) the nature of the cosmetic /dermatological formulation. Three specific assumptions were made: firstly,steady-state transport across the skin was achieved despite application of a finitedose of chemical; secondly, vehicle effects were small relative to the precision ofthe prediction; and, thirdly, each formulation could be treated as an oil-in-wateremulsion, in which only that fraction of the chemical in the aqueous phase wasavailable to partition into the stratum corneum. A database of 101 skin experiments involving 36 chemicals was analysed.ex vivo humanResults values was less than a factor 5; when the aforementioned corrections were notused, on the other hand, only 26% of the data was well predicted. The modelwas successfully applied to predict skin absorption of two compounds notincluded in the database, for which vehicles have been measured.For 91% of the data, the difference between predicted and experimentalin vitro percutaneous penetration from cosmeticConclusion into and through the skin from a cosmetic or dermatological formulation.A model has been developed to predict the mass of a chemical absorbed