Naturally occurring, long chains of skin lipids (fats) that are major structural components of skin’s outer layers. Skin as a barrier system inhibits water movement via its extracellular matrix, which has a unique composition of 50% ceramides, 25% cholesterol, and 15% free fatty acids. Together, these lipids form what researchers refer to as “crystalline lamellar structures.” [1, 2, 3]
Ceramides are necessary for their water-retention capacity as well as for barrier repair and cell regulation. Adding ceramides to skincare products can help restore the skin’s barrier. [4, 5, 6]
Nine different ceramides have been identified in skin, some of which are used in skincare products. On a skincare product ingredient label, you’ll see those listed as ceramide AP, ceramide EOP, ceramide NG, ceramide NP, ceramide NS, phytosphingosine (which can produce numerous ceramides in skin), and sphingosine. 
The ceramides used in skincare products typically are derived from plants or are synthetic; there is no research showing that either form is preferred over the other. However, the chain length of synthetic ceramides can be controlled, while the chain length of plant or of animal-derived ceramides cannot be controlled. The benefit of controlling the chain length is that it can be made a “better fit” when the ceramide chain is applied to skin cells in need of help. 
- Kwon Y, Kim C, Youm J, Gwak H, Park B, Lee S, Jeon S, Kim B, Seo Y, Park J, et al. Novel synthetic ceramide derivatives increase intracellular calcium levels and promote epidermal keratinocyte differentiation. J Lipid Res. 2007;48(9):1936-43.
- Vielhaber G, Pfeiffer S, Brade L, Lindner B, Goldmann T, Vollmer E, Hintze U, Wittern K, Wepf R. Localization of ceramide and glucosylceramide in human epidermis by immunogold electron microscopy. J Invest Deratol. 2001;117(5):1126-36.
- Schwarz T. Biological effects of UV radiation on keratinocytes and Langerhans cells. Exp Dermatol. 2005;14(10):788-9.
- Choi M, Maibach H. Role of ceramides in barrier function of healthy and diseased skin. Am J Clin Dematol. 2005;6(4):215-23.
- Proksch E, Fölster-Holst R, Jensen J. Skin barrier function, epidermal proliferation and differentiation in eczema. J Dermatol Sci. 2006;43(3):159-69.
- Geilen C, Barz S, Bektas M. Sphingolipid Signaling in Epidermal Homeostasis. Skin Pharmacol Appl Skin Physiol.. 2001;14:261-271.
- Meckfessel M, Brandt S. The structure, function, and importance of ceramides in skin and their use as therapeutic agents in skin-care products. J Am Acad Dermatol. 2014;71(1):177- 84.
- Mojumdar E, Kariman Z, van Kerckhove L, Gooris G, Bouwstra J. The role of ceramide chain length distribution on the barrier properties of the skin lipid membranes. Biochim Biophys Acta. 2014;1838(10):2473-2483.