Function of ceramides in the skin and its relationship with skin disease.

The skin is a vital organ that protects the body from external insults. Ceramides, the major lipid components of the skin, are synthesized through three main pathways: de novo synthesis, sphingomyelin hydrolysis, and the salvage pathway. Ceramides are crucial for maintaining the skin barrier and hydration, and their deficiencies are associated with various skin diseases such as atopic dermatitis, psoriasis, and Netherton's syndrome. In the cosmetic industry, ceramides are used for skin barrier repair and moisturization. However, their poor water solubility necessitates the development of effective delivery systems. Alternatively, exogenous substances can be utilized to promote ceramide synthesis in skin. Therefore, elucidating the mechanisms by which ceramides influence the skin barrier and hydration, and developing ceramide-containing cosmetic products based on these mechanisms, represent promising research directions for improving skin health.