Skin biology.

The development of topical drug delivery systems has recently gained significant interest due to the ease of administration and lesser risks of systemic toxicity. The development of these new technologies utilizes the properties of the structure and function of the skin. The stratum corneum plays the largest role in affecting drug permeation, as the corneocytes and lipid matrix in this layer effectively prevent the diffusion of large molecules. In this review, we introduce the structure and function of the skin as it relates to topical drug delivery.