Abstract: AimTo investigate the penetration kinetics of xanthotoxin in human skin and stratum corneum. MethodsThe penetration experiments were accomplished by the deposit of ethanolic xanthotoxin solution onto human skin and stratum corneum mounted on Franz cells. The diffused xanthotoxin in the receptor solution (1.4% human serum albumin) and the retained amount in the skin and in the stratum corneum after 24 h exposure were quantified by using high performance liquid chromatography. ResultsXanthotoxin flux was increased with the concentration deposited onto the human skin, and when the concentration is above 2.5 mg·mL^-1, there is no influence on the xanthotoxin flux. Similar results were obtained from the stratum corneum. And the peak time for the flux in the stratum corneum was preceded about 6 h earlier than that of the whole human skin. The retained xanthotoxin amount after 24 h exposure in the skin and in the stratum corneum increased according to the concentration deposited and has the tendency to saturate. The lag time of ethanolic xanthotoxin solution in the whole human skin is significantly higher than that in the stratum corneum (P<0.05). ConclusionThe characteristics of penetration kinetics of xanthotoxin will provide the information for concentration choice of topical formulation and give a reference for ultra violet A (UVA) irradiation time confirmation.