Skin ceramides are amides of sphingosine and ω-hydroxy fatty acids, with the hydroxyl group esterified with linoleic acid. They are colourless wax-like substances that are practically insoluble in water. They are usually available in powder form. They can be isolated from the above mentioned natural sources, but are mostly produced today by synthesis. Ceramides are the main intercellular lipids of the stratum corneum and are crucial for the proper organisation of lipid lamellar phases. They are classified in the group of sphingolipids.

Source: Modern Cosmetics - Dr. Damjan Janeš and Dr. Nina Kočevar Glavač