Moisturization
The epidermis normally contains 10 to 20% of water. Skin containing less than 10% can be considered dehydrated.
This may be due to a number of factors, including problems with the keratinocytes or damage to the outer layers of the skin, both of which allow more water to escape; or destruction of the natural moisturizing molecules of the skin such as hyaluronic acid or NMF.
Because water is needed for vital processes within the skin, dehydrated skin may lose its ability to repair itself as easily as well-hydrated skin. Dry skin is a term applied to skin that is tight, rough, scaly, and cracked.
Actives and even formulation excipients such as emulsifiers can provide or enhance the moisturizing properties of a formulation.