ABSTRACT
The human skin is exposed to many topical agents, either intentionally or by accident. The variety of these foreign agents such as xenobiotics, reflects the variety of their intended uses: cosmetics are intended, in theory, to decorate the skin rather than penetrate it. This chapter demonstrates that many exogenous compounds are metabolized in skin. It reviews the existence of enzymes that are capable of metabolizing cutaneous xenobiotics and some of the factors regulating their activity. The chapter also reviews the recent work documenting the metabolism of commonly prescribed drugs and environmental agents on the skin. The induction of enzymes that metabolize xenobiotics may increase the rate and/or amount of metabolites produced. In contrast to induction, the inhibition of enzymes must also be considered. Inhibition of the cutaneous metabolism of xenobiotics has several theoretical advantages. For example, selectively inhibiting an enzyme may increase the overall percutaneous absorption of a particular medication.
