ABSTRACT
The skin is constantly exposed to environmental factors that might influence the integrity of the skin barrier. Chemicals and pharmaceuticals can penetrate into the skin and have a local effect, or they may penetrate the skin, enter the circulation, and exert a general effect. In penetrating the skin they may also be altered by local metabolism. In toxicology, the percutaneous route for entrance of chemicals into the body has been underestimated [1]. For example, penetration through the skin is the main route by which pesticides enter the body [2]. Today it is recognized that stratum corneum is the main barrier to penetration and that the main route for penetration into and through the skin is via the lipid-rich intercellular space of stratum corneum [3]. Skin diseases characterized by disturbed keratinization, (e.g., psoriasis, ichthyosis) or by changes in the lipid composition (e.g., atopic dermatitis) do have a detectable defect in the barrier function. A common environmental exposure (at work, at home, and in the community) is to different types of solvent. This chapter discusses both skin diseases in which barrier properties are altered and the effects of solvents. The development of systems for percutaneous drug delivery, which calls for the addition of penetration enhancers to a product, [3-6], is not extensively explored in this text.
