In some respects, “skin barrier” is an unfortunate term as the whole skin is a barrier. For people interested in eczema, the skin barrier is a specific, very thin, layer towards the outer edge of the epidermis, just below the very outside of the skin. Its purpose is to restrict water flow from the skin. We all lose water through the skin. If the skin barrier is fully functional, very little water passes through. If the skin barrier is sub-optimal, more water is lost. Individuals perceive this as dry skin and, by the time that sensation is felt, there are already tiny, invisible cracks in the epidermis which go through the skin barrier.
Biochemical Components Of The Skin Barrier
There are two main biochemical components of the skin barrier: A double layer of ceramide lipid, which is specialised fat made by the skin cells just before they dry up and fall off the surface of the outer skin. Strong detergents and solvents can wash this fat from the barrier and higher levels of the stress hormone cortisol reduce the ceramide made by the skin cells. Special water-repelling amino acids that are derived from the filaggrin protein which is also made by the skin cells. This protein performs several other functions before it finally breaks into hygroscopic amino acids. Inflammation in the skin from any cause reduces the cells’ ability to read the filaggrin gene. In this case, less of the protein is made, which results in less amino acids. Therefore, a person who feels stressed about red patches of skin inflammation is very likely to have reduced skin barrier function and the affected areas of skin will feel dry. Many products sold for application to dry and red skin contain paraffin, a substance which unfortunately separates the two layers of ceramide fat, making things worse. What can you do? Well, you can begin by using products which are free from paraffin.
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