Skin barrier function and stratum corneum hydration

Under normal circumstances, epidermis must be as impermeable as possible except for a small amount of water loss to hydrate the outer layers of the SC. Although all living cells require water to function, some “dead” cells also require water to be metabolically active. As it is the case of corneocytes, epidermis must retain sufficient water to (a) hydrate the outer layers of the SC to maintain its flexibility and deformability and (b) to provide enough water to allow enzyme reactions that facilitate SC maturation events, together with corneodesmolysis and ultimately desquamation (Rawlings, 2006).