“…Though the stratum corneum is the thinnest layer of the skin at the preferred application sites it is the rate limiting structure for transepidermal drug transport. Disregarding the less pronounced drug penetration via pores (transglandular, transfollicular), two types of transepidermal transport can be distinguished: the transcellular and the intercellular route [2]. In case of the first mentioned type the drug has to pass both, the intercellular lipid layers and the hydrophilic Scheler et al …”