Xerosis, or dry skin, is a common occurrence in winter climates, particularly in conditions of cold air, low relative humidity, and indoor heating. Xerosis can affect anyone, but it tends to be more severe in certain persons, especially those with a hereditary predisposition. Modern lifestyles are also contributing factors. In Western societies, people tend to over bathe and often live and work in overheated spaces.

The word “dry” is sometimes misapplied. Skin that appears to be dry (i.e., that shows a buildup of scale) may not always be suffering from a lack of water but rather from an over adherence or hyperproliferation of scale. Over adherence of scale occurs in patients with ichthyosis (see discussion in Chapter 4: Eczema in Infants and Children). Hyperproliferation of scale is noted in atopic dermatitis, psoriasis, seborrheic dermatitis, and common dandruff.