Stratum corneum hydration components

The stratum corneum (SC) is the skin's outermost layer, functioning as a critical biosensor and barrier against environmental stressors (Source: StatPearls: NBK513299). Water within the SC is not merely a solvent but a structural component that maintains the flexibility of keratin filaments and enables the activity of hydrolytic enzymes responsible for desquamation (Source: PubMed: 15171757). Polar groups found on Natural Moisturizing Factors (NMF), such as amino acids and urea, as well as the polar head groups of intercellular lipids like ceramides, serve as the primary binding sites for this water (Source: Journal of Clinical and Aesthetic Dermatology: PMC4885180). In conditions such as xerosis, atopic dermatitis, and psoriasis, the concentration of these polar groups or the integrity of the lipid matrix is diminished, leading to increased transepidermal water loss (TEWL) and skin fragility (Source: PubMed: 24656726). Therapeutic agents like humectants (e.g., glycerin) directly target these polar groups to attract and retain moisture, while occlusives (e.g., petrolatum) create a physical barrier to prevent evaporation (Source: PMC4885180). Restoring the hydration of the SC and the functionality of its polar components is essential for repairing the skin barrier and alleviating inflammatory symptoms associated with dry skin diseases.

Other names

Water in the stratum corneum and polar groups of corneocyte proteins/lipidsNatural Moisturizing Factor (NMF)Skin barrier hydrationCorneocyte-lipid matrixEpidermal water content

Humectants (e.g., glycerin, urea) attract and bind water to polar groups within the corneocytes and lipid matrix; occlusives (e.g., petrolatum) form a hydrophobic film to prevent transepidermal water loss; emollients (e.g., ceramides) integrate into the intercellular lipid bilayers to restore barrier integrity and reduce evaporation (Source: PMC4885180).