Effect of zinc pyrithione on mitotic activity in normal human skin.

Two concentrations (0.02% and 0.002%) of zinc pyrithione (ZPT) in water and a water control were applied to normal forearms - both on normal skin (six subjects) and also where the skin had been stripped to the 'glistening layer' (six subjects) with adhesive tape. Measurements of labelling index (LI), mean epidermal thickness (MET), mean stratum-corneum thickness (MSCT), total epidermal thickness (TET) and basal/granular cell ratio (B/G) showed no significant differences between the three treatments on normal skin or the parameters studied in stripped skin. It is concluded that ZPT has no effect on epidermal renewal in normal skin in vivo.