Scientists are uncovering the important role that ceramides play in the barrier function of the skin. The top layer of the skin is the epidermis, and the top layer of the epidermis is the stratum corneum (SC). Even though the SC is very thin -- 10-30 mm or one-tenth the thickness of a piece of paper -- it is the main barrier of the skin. It keeps chemicals that come in contact with the skin from absorbing into the body, and it keeps water inside the skin from leaching out.
Lipids in the SkinThe SC contains three types of lipids -- ceramides, cholesterol and free fatty acids. These lipids have different chemical compositions and different functions throughout the body. There are nine different types of ceramides in the SC, conveniently named ceramide 1 through ceramide 9, and they account for 40-50% of the lipids in this outermost layer.
Ceramides and Skin DiseaseScientists have learned that people who have eczema have significantly fewer ceramides in their SC. On the other hand, people with psoriasis (another itchy, flaky rash sometimes confused with eczema) have the same number of ceramides compared to people with normal skin. However, the psoriasis-sufferers have less ceramide 1, 3, 4, and a sub-set of 5 and 6; and more ceramide 2 and another sub-set of 5.
Replacing Ceramides Improves EczemaRecent studies have shown that lipids can be replaced with topical preparations. Interestingly, all three lipids have to be replaced at a certain ratio to restore the barrier function of the skin. If the incorrect balance of lipids is applied, it actually takes longer for the skin to heal. The healing effect of ceramides has been studied in eczema, but there are no studies yet for psoriasis.
Moisturizers with Ceramides - Not All the SameThere are several moisturizers that claim to have ceramides in their ingredients, but these are just regular moisturizers unless they can show:
- The moisturizer also contains cholesterol and free fatty acids
- The ratio of these three ingredients is correct
Berardesca E, et al. "Evaluation of efficacy of a skin lipid mixture in patients with irritant contact dermatitis, allergic contact dermatitis or atopic dermatitis: a multicenter study." Contact Dermatitis. 5(2001):280-5.
Chamlin, Sarah, et al. "Ceramide-dominant barrier repair lipids alleviate childhood atopic dermatitis: Changes in barrier function provide a sensitive indicator of disease activity." Journal of the American Academy of Dermatology 47(2002): 198-208.
Choi, Myeong Jun, and Howard Maibach. "Role of Ceramides in Barrier Function of Healthy and Diseased Skin." American Journal of Clinical Dermatology 6(2005): 215-22.
Coderch L, et al. "Efficacy of stratum corneum lipid supplementation on human skin." Contact Dermatitis. 3(2002):139-46.
Kucharekova M, et al. "Effect of a lipid-rich emollient containing ceramide 3 in experimentally induced skin barrier dysfunction." Contact Dermatitis. 6(2002):331-8.