Percutaneous absorption and age. Implications for therapy.

Human skin changes dramatically with increasing age. Morphological, physiological, and biochemical changes within the tissue have been investigated and documented. Considerable interest in transdermal drug delivery to produce systemic effect has occurred in recent years. However, it is not known whether the penetration barrier of aged skin changes. Morphological and physiological changes in aged skin may affect the percutaneous absorption of compounds and thus their potential for localised, as well as systemic, efficacy. This article reviews the published literature on skin aging changes from adulthood to old age, collates these changes with clinical implications pertinent to the practising dermatologist, reviews the existing data supporting a change in the barrier function of human skin with increasing age, and comments on the relevance of conclusions previous investigators have drawn from their studies.