Ever heard of ceramides? Don’t worry if you haven’t, we've got you covered.
Ceramides are a family of lipids (commonly called fats, although technically fats are a type of lipid1) that help to form the skin barrier.2 This barrier (the very top layer of the skin, also known as the stratum corneum), is made up of dead skin cells, squashed down flat and embedded in a matrix of lipids.2,3 It looks a bit like bricks and mortar, with the dead cells as the bricks and the lipid matrix as the mortar holding it all together. In healthy skin, ceramides make up approximately 40-50% of this lipid matrix. Other components are cholesterol (around 25%) and free fatty acids (10-15%).4
Ceramides have a lot of interesting attributes, like being one of the most hydrophobic lipids found in membranes2 (that means they really dislike water). But they're made up of two parts – one half that really dislikes water, and one half that really likes it. Because of this dual-structure, the parts that dislike water all face each other and the parts that love water sit in neat rows on the outside, helping form the protective barrier layer of our skin and trapping moisture inside.1
Ceramides are a family of lipids that help to form the skin barrier.2
In skin prone to eczema, this barrier layer doesn’t work as well as it should and moisture can escape.5 One of the reasons for barrier dysfunction is that some of the ceramides are reduced.5 It makes sense when you think about it – as the number of water-disliking molecules gets lower they can't form neat rows, letting water sneak past.
In human skin, 11 types of ceramides have been identified so far.2 For people with eczema, two of these are particularly important. Ceramide 1 (also known as Cer EOP) is the most deficient.6,7 Ceramide 3 (also known as Cer NP) is the main contributor to water loss through the epidermis.6,7 Now that researchers know this, they're developing products that can help replenish the level of ceramides in the skin.
References
1. "Thompson TE, Encyclopaedia Britannica, Lipid [internet], 2017 [published 2017 November 6; cited 2018 May 25]. Available from: https://www.britannica.com/science/lipid
2. Novotny J, Hrabàek A, Vávrová K. Synthesis and structure-activity relationship of skin ceramides. Curr Med Chem. 2010; 17(21):2301–24.
3. Janssens M, van Smeden J, Gooris GS, Bras W, Portale G, Caspers PJ, et al. Increase in short-chain ceramides correlates with an altered lipid organization and decreased barrier function in atopic eczema patients. J Lipid Res. 2012; 53:2755–2766.
4. Zeichner JA and Del Rosso D. Multivesicular Emulsion Ceramide-containing Moisturizers: An Evaluation of Their Role in the Management of Common Skin Disorders. J Clin Aesthet Dermatol. 2016; 9(12):26-32.
5. Sajic D, Asiniwasis R, Skotnicki-Grant S. A Look at Epidermal Barrier Function in Atopic Dermatitis: Physiologic Lipid Replacement and the Role of Ceramides. Skin Therapy Lett. 2012; 17(7):6-9.
6. Di Nardo A, Wetz PW. Atopic dermatitis. In: Leyden JJ, Rawlings AV, editors. Skin Moisturization. New York: Marcel Dekker; 2002. pp. 165–178.
7. Di Nardo A, Wertz P, Giannetti A and Seidenari S. Ceramide and cholesterol composition of the skin of patients with atopic dermatitis. Acta Derm Venereol. 1998; 78(1):27-30.