Stratum corneum (SC) (SC)

The stratum corneum is the outermost layer of the epidermis, serving as the body's primary physical and permeability barrier between the internal environment and the external world (StatPearls, 2023). Often described by the "bricks and mortar" model, it consists of protein-rich corneocytes (bricks) embedded in a complex extracellular lipid matrix (mortar) composed of ceramides, cholesterol, and free fatty acids (Journal of Investigative Dermatology, 2012). Its primary biological function is to prevent excessive transepidermal water loss and protect against environmental insults, including pathogens, allergens, and UV radiation (NIH, 2021). Dysfunction of this barrier is a hallmark of various dermatological conditions, such as atopic dermatitis and psoriasis, where impaired lipid composition or filaggrin deficiency leads to inflammation and increased susceptibility to infection (PubMed, 2020). Therapeutic interventions focus on barrier repair through the application of physiological lipids, humectants, and occlusives to restore homeostasis and improve skin health (Clinical, Cosmetic and Investigational Dermatology, 2015). Understanding the stratum corneum is also critical for optimizing topical drug delivery, as it represents the rate-limiting step for the absorption of most dermatological treatments.

Other names

Epidermal barrierSkin barrierHorny layerPermeability barrierEpidermal permeability barrier

Drugs targeting the stratum corneum act by replenishing essential lipids to restore the lamellar structure, using occlusives to prevent water loss, or employing humectants to attract moisture into the corneocytes (StatPearls, 2023). Keratolytic agents promote the shedding of the outer layer by breaking down desmosomal connections between corneocytes (Journal of Investigative Dermatology, 2012).