ABSTRACT
The traditional view of the stratum corneum regards this outer layer of the epidermis to be a relatively impermeable and highly resilient tissue. In fact, up to the mid-1970s, the stratum corneum was considered a metabolically inert, homogenous tissue, analogous to plastic wrap. According to this model, passive transdermal permeation is governed solely by the physicochemical properties of this seemingly homogeneous tissue (Scheuplein and Blank, 1971). Based on this view, the permeability barrier can be reproduced in vitro with isolated stratum corneum sheets, regardless of whether cadaver-derived, frozen-thawed, or freshly obtained tissues are employed for permeability studies.
