Many products provide ceramides, but at very low concentrations because of their high price. Ceramides are a family of lipid molecules; a ceramide is composed of sphingosine and a fatty acid.
Ceramides are found in high concentrations within the cell membrane, but they have more than a structural role. They are signaling molecules involved in the regulation of cellular differentiation, proliferation, and apoptosis.
The skin acts as a protector against water loss and physical, chemical, and biological attack. To perform its protective task, the skin must have a resistant barrier. This barrier is provided by the 'horny layer' stratum corneum, the outermost layer of the epidermis. The stratum corneum consists of anuclear flattened cells, the corneocytes, embedded in a lipid mixture consisting mainly of a lamellar structure of ceramides, cholesterol, and fatty acid. Insufficient formation or loss of skin lipids can result in an increased water loss and increased penetration of harmful compounds from the environment, both of which often cause skin dryness and skin sensitivity.