Hairless mouse skin is limited as a model for assessing the effects of penetration enhancers in human skin.

The permeability coefficient of 5-fluorouracil through human abdominal and hairless mouse skins was used as an indicator of the relative effects of 12-h pretreatment of the skins with either penetration-enhancer mixtures [including laurocapram (Azone), decylmethylsulfoxide, oleic acid, and propylene glycol] or saline (control). After treatment with saline, fluxes of 5-fluorouracil through the two skin types were similar, but the mouse skin showed exaggerated responses to all the penetration-enhancer formulations. There was no consistent relationship between enchancer effects on the two skin types, and we conclude that the hairless mouse model should not be used to predict the effects of penetration enhancers in human skin. After treatment with saline, hairless mouse skin sharply increased in permeability after approximately 50 h hydration, suggesting that the stratum corneum had started to disrupt, whereas the flux through human skin remained unchanged.