The Epidermal Barrier and Strategies for Surmounting It: An Overview

As the largest organ comprising more than 10% of the body mass in humans, the skin serves as the physical barrier for the body. The bulk of it is made up of dermis, but it is the epidermis that is vested with the function of producing, maintaining and renewing the superficial and crucial compartment, the stratum corneum (SC). This layer of terminally differentiated keratinocytes provides the physical basis for several types of barrier functions including: barrier to water permeability, penetration of xenobiotics, and microbial and parasitic invasion. Additionally the SC barrier helps to maintain the integrity of other components by providing 1) defense against UV radiation and free radical injury, 2) the immune barrier and 3) crucial skin functions such as thermoregulation, waste elimination and sensory transduction (heat, cold, pain, etc.).