Acid mantle (acid mantle) is a very important on the skin composition of the key, the human skin has a layer of natural protective film, also known as the weak acid layer (ie acid cover), the naked eye can not see the natural film, the purpose of preventing skin Bacteria or contaminants. The stratum corneum is responsible for maintaining adequate water in the body, to avoid excessive evaporation of water through. When we use a soap bath, shampoo, it will wash off this layer of acid grease. This is why most people's bath milk, shampoo add moisturizing formula, is to replace the scrubbed out of the protective layer, washed away the grease at least 12 hours before they will add back. When the stratum corneum peel will cause the skin dry, peeling, more serious and even there will be prickle and rash.