Stratum Corneum

The stratum corneum is the outermost layer of the epidermis, serving as the primary barrier between the body and its external environment. It consists of 15–20 layers of flattened, dead cells (corneocytes) embedded in a lipid matrix composed mainly of ceramides, cholesterol, and fatty acids. It acts as a physical and chemical barrier, prevents water loss, protects against mechanical stress and chemical insults, contributes to immune defense, and maintains an acidic pH. Desquamation and barrier repair are key biological processes involving the stratum corneum. It is both a target for topical therapies and a major obstacle for transdermal drug delivery.