transepidermale

Transepidermale is an adjective used to describe processes or transport that occur across the epidermis, the outermost layer of the skin. In physiology and dermatology, it refers to movement through or across the epidermal barrier, particularly the stratum corneum, which governs water and solute diffusion.

A central context is transepidermal water loss (TEWL), the diffusion of water from the body through the epidermis to the external environment. TEWL is widely used as an objective measure of skin barrier integrity and moisturization; higher TEWL values indicate a compromised barrier and are associated with dry skin, irritation, and inflammatory skin conditions.

Transepidermal processes also encompass trans-epidermal drug delivery, wherein substances penetrate the skin barrier to reach systemic circulation or local targets. These processes depend on the physicochemical properties of the compound, skin hydration, lipid organization in the stratum corneum, and formulation factors. Methods to enhance transepidermal delivery include formulation strategies, chemical penetration enhancers, and physical technologies that modify barrier function, such as microneedles.

Measurement and study of transepidermal transport rely on devices that quantify water vapor flux for TEWL or pharmacokinetic approaches for evaluating drug permeation. The concept is central to skin biology, clinical dermatology, and cosmetic science because the epidermal barrier controls water loss and the entry of external agents.

Etymology notes: the term combines trans- meaning across with epidermis, and is used in several languages to describe cross-skin phenomena. See also epidermis, stratum corneum, TEWL, transdermal drug delivery.