A well hydrated skin shows less wrinkles and is often less prone to irritation. A sensitive skin is the result of a disrupted skin barrier; one of which the intercellular lipids have some defects. As a result, not only irritants or allergens can penetrate the skin (from the outside to the inside), but water can also easily evaporate from the skin (from the inside to the outside). If this happens, skin dehydration occurs.
In addition, the moisture balance is also determined by molecules that can attract and transport water. Defects in these molecules also lead to a disturbed moisture balance and result in a dry, dehydrated skin.
Some investigates whether you have mutations in the genes that help keep the skin barrier intact and help control the moisture balance; namely Fillagrin (FLG) and Aquaporin-3 (AQ3)