Average thickness of the removed stratum corneum versus number of tape strippings, for a representative subject. Thickness of removed stratum corneum, e, was calculated for both values of stratum corneum density (1 and 1.33 g cm−3 as , where S is the stripping surface, Δm the mass of stratum corneum removed from each tape stripping and ρSC the stratum corneum density (grey cross symbols, thickness of SC removed for SC density 1 g cm−3; black squares, average thickness of SC removed; open squares, thickness of SC removed for SC density 1.33 g cm−3).