Immunologic reactions triggered during irritant contact dermatitis.

This article discusses a novel approach to the understanding of human skin barrier function with particular emphasis on the immunologic consequences of barrier perturbation. Clearly, the most important homeostatic function of the skin is to restrict the ebb and flow of water molecules to maintain a physiological balance with respect to hydration between the inside of the body and the external environment. The early investigators of barrier function initially focused on defining the biophysical properties of the stratum corneum and integrating the concepts of Singer and Nicholson1 into various models such as the brick and mortar concept by Elias2 and the domain mosaic model by Forslind.3 Rather than examining lipids, cholesterol, and free fatty acids in the stratum corneum, the authors have been interested in characterizing the types of specialized proteins termed cytokines that are intimately linked to the barrier structure and function of human and rodent skin.4 Cytokines are key mediators of inflammatory and immunologic reactions throughout the body; how these cytokines are modulated in response to changes in barrier function provides new insights that pass beyond the physical/mechanical protective nature of skin into the immunologic sphere of influence for barrier function and cutaneous homeostasis.