What causes dry skin and why in the winter is it so bad?

The skin is the site of evaporation of water. It is our own natural air-conditioner. In the winter when the humidity is low and the air is very dry, the skin becomes itchy because it also becomes dry and, in some patients, very scaly. Certain conditions like diabetes, high fevers, or alcoholism, where the body becomes dehydrated means that the skin of such patients will itch more.