Stratum corneum water (SC water)

Water molecules in the stratum corneum (SC) are fundamental to the skin's biological and mechanical properties, acting as a critical plasticizer for keratin and a necessary medium for enzymatic activity (Verdier-Sévrain & Bonté, 2007, J Cosmet Dermatol). The SC requires a minimum water content to maintain flexibility and facilitate the proteolytic degradation of desmosomes, a process known as desquamation; insufficient hydration leads to the accumulation of corneocytes and the appearance of dry, scaly skin (Rawlings & Harding, 2004, Dermatol Ther). In dermatological therapy, water is targeted through the use of humectants, which chemically bind water molecules via hydrogen bonding, and occlusives, which prevent their escape into the environment (Fluhr et al., 2008, Skin Pharmacol Physiol). Maintaining optimal water levels is essential for treating conditions like atopic dermatitis and xerosis, where the skin barrier is compromised and transepidermal water loss is elevated (Bouwstra & Ponec, 2006, Biochim Biophys Acta). As a therapeutic target, SC water is unique because it is a solvent and structural component rather than a signaling protein, yet its modulation is the primary goal of most topical moisturizing agents.

Other names

Skin hydrationCorneocyte water contentIntracellular water of the stratum corneumTransepidermal water

Humectants attract and bind water molecules within the stratum corneum via hydrogen bonding to increase hydration, while occlusives form a hydrophobic film on the skin surface to physically block transepidermal water loss (TEWL).