Skin hydrolipidic film (HLF)

The skin hydrolipidic film is a complex, invisible emulsion located on the surface of the stratum corneum, composed primarily of sebum from sebaceous glands and sweat from sudoriferous glands. It serves as the body's primary physiological barrier, maintaining skin hydration by limiting transepidermal water loss and providing an 'acid mantle' (pH 4.5–5.5) that inhibits the colonization of pathogenic microorganisms. In addition to physical and chemical protection, the film contains antioxidants like squalene and vitamin E that neutralize environmental stressors such as UV radiation. Disruption of this film is a hallmark of various dermatological conditions, including atopic dermatitis, xerosis, and acne, where an imbalance in lipid or aqueous components leads to increased sensitivity and inflammation. While not a single molecular target like a receptor or enzyme, the hydrolipidic film is therapeutically 'targeted' through the use of emollients, humectants, and barrier-repairing agents that aim to restore its integrity. Drugs and cosmeceuticals often interact with this layer by replenishing essential lipids (e.g., ceramides, fatty acids) or by using penetration enhancers to bypass its protective structure for deeper drug delivery.

Other names

Acid mantleHydrolipidic layerSkin surface lipid filmSSL filmHydrolipid barrier

Barrier restoration, Occlusion, Humectancy, pH acidification, Lipid replenishment