"The natural function of the skin is to protect the body from environmental influences. The main barrier of the skin is located in the stratum corneum, the outer layer. The stratum corneum requires ceramides, cholesterol and fatty acids to provide barrier function. These three are the most important components of intercellular lipids(spaces) in the stratum corneum and are fundamental in maintaining the skin barrier properties. Their content is decreased in some skin diseases. A total amount of reduced ceramides and increased water loss could be responsible for functional abnormalities of atopic dermatitis. It is well known that ceramides play an important role in structuring and maintaining the permeability barrier function of the skin."
says we need three things to provide barrier function;