Ceramiden

Ceramides are a family of lipid molecules consisting of a fatty acid amide-linked to a long-chain base called sphingosine, forming a class of sphingolipids. They are among the main lipids of the skin’s stratum corneum and play a key role in the skin’s barrier function.

Ceramides are not a single compound but a group of related molecules that vary in the sphingoid base and the length and type of the amide-linked fatty acid. In human skin, important subclasses include ceramides NP, NS, NH, AS, and others, which together contribute to the formation of the lamellar lipid matrix that surrounds corneocytes.

Biosynthesis occurs in keratinocytes through de novo synthesis and the processing of glucosylceramides. Enzymes such as serine palmitoyltransferase and ceramide synthases (CerS) are involved, followed by modifications that produce the mature ceramide pool in the stratum corneum.

Functionally, ceramides help organize the stacked lipid lamellae that limit water loss and protect against irritants and microbes. They also participate in cellular signaling related to differentiation and inflammatory responses.

Clinically, reduced levels of ceramides are associated with dry skin, aging, and some inflammatory dermatoses, including atopic dermatitis and ichthyosis. Topical ceramides are widely used in moisturizers and therapeutic preparations to restore barrier function and improve hydration; they are generally well tolerated.

Ceramides are produced endogenously, and formulations use plant- or synthetically derived ceramides to replenish the skin’s lipid barrier. See also sphingolipids and stratum corneum.