Skin surface hydration

Skin surface hydration refers to the water content in the outermost layer of the skin, the stratum corneum, and is essential for maintaining skin barrier integrity, mechanical flexibility, and normal cell shedding[1][3][5][7][9]. This hydration state depends on natural moisturizing factors (NMF), intercellular lipids (such as ceramides, fatty acids, and cholesterol), aquaporins (e.g., aquaporin-3), and humectant compounds that attract water[1][5][7]. Dehydration of the skin surface leads to dry, flaky, and less elastic skin and is associated with dermatological conditions such as eczema and psoriasis[7]. Hydration is measured by biophysical techniques (e.g., corneometry, TEWL) and is improved by moisturizers containing humectants, occlusives, and emollients[1][6][7]. Key Point: "Skin surface hydration" is not a canonical molecular/therapeutic target but a physiological state influenced by various molecules and structures in the skin[1][5][7].

Other names

Skin hydrationStratum corneum hydrationSkin moistureEpidermal hydration

Humectants draw and retain water within the stratum corneum[1][5][6][7] Occlusives form a barrier to reduce water evaporation from the skin surface[1] Emollients smooth the skin surface and fill in gaps between corneocytes Barrier repair agents increase synthesis or repair of skin lipids (e.g., ceramides, fatty acids)[4]