Xerosis (also called dry skin, asteatosis, xeroderma, or ashy skin) refers to a condition of rough, dry skin texture with associated fine scales. Xerosis is often pruritic. The pathogenesis involves a decrease in the amount of lipids in the stratum corneum and a deficiency in the water-binding capacity of this layer.

Xerosis is associated with a number of environmental factors and/or disease states, such as low humidity, frequent bathing, harsh soaps, ichthyoses, atopic dermatitis, hypothyroidism, Down syndrome, menopause, diabetes, renal failure, malnutrition and malabsorptive states, HIV, lymphoma, liver disease, Sjögren syndrome, carcinomatosis, and certain drugs (diuretics, statins, retinoids, and anticholinergic drugs).

The incidence of xerosis increases with age; nearly all individuals older than 60 have some degree of xerosis. Any part of the skin can be affected, although areas with the fewest sebaceous glands are most frequently affected (hands, feet, lower extremities, and forearms).