Fig. 4

Steroids measured by Scheuplein, Johnson and Anderson are grouped in clusters. It is apparent that these researchers used compounds with different molecular weight classes and performed experiments with different skin layers; in green: Scheuplein steroids, in blue: Johnson steroids, in red: Anderson steroids; the layer of the skin that was used is shown by the shape of the marker – square: epidermis, diamond: stratum corneum. Scheuplein steroids, in blue: Johnson steroids, in red: Anderson steroids; the layer of the skin that was used is shown by the shape of the marker – square: epidermis, diamond: stratum corneum.