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