ceramides

Ceramides are a family of waxy lipid molecules composed of a fatty acid amide-linked to a sphingoid base, usually sphingosine. They are a major component of the stratum corneum, forming part of the lipid matrix that helps hold skin together. Ceramides vary in chain length and saturation, producing a diverse ceramide profile across tissues.

In humans, ceramides contribute to the skin’s permeability barrier, helping to limit transepidermal water loss and maintain hydration. They also participate in signaling pathways related to cell differentiation and apoptosis; in the skin, they are produced by keratinocytes and are present in the natural moisturizing factor.

Ceramides are synthesized de novo through a pathway initiated by serine palmitoyltransferase and involve subsequent steps, or they can be generated by hydrolysis of sphingomyelin. They can be degraded by ceramidases to form sphingosine and free fatty acids. Levels of ceramides decline with aging and in certain skin disorders, such as atopic dermatitis and psoriasis, contributing to barrier dysfunction.

In cosmetics and dermatology, topical ceramides are used to replenish the skin’s lipid barrier, often in formulations with cholesterol and free fatty acids to mimic the natural lipid matrix. They are generally well tolerated. In medical research, ceramide signaling is studied for roles in inflammation and disease, with work spanning preclinical and clinical settings.