Atopic dermatitis, also known as atopic eczema, is an atopic, hereditary, and non-contagious skin disease characterized by chronic inflammation of the skin.

The skin of a patient with atopic dermatitis reacts abnormally and easily to irritants, food, and environmental allergens and becomes red, flaky and very itchy. It also becomes vulnerable to surface infections caused by bacteria. The skin on the flexural surfaces of the joints (for example inner sides of elbows and knees) are most commonly affected regions in people.

Atopic dermatitis often occurs together with other atopic diseases like hay fever, asthma and conjunctivitis. It is a familial and chronic disease and its symptoms can increase or disappear over time. Atopic dermatitis in older children and adults is often confused with psoriasis. Atopic dermatitis afflicts humans, particularly young children; it is also a well-characterized disease in domestic dogs.

Although there is no cure for atopic eczema, and its causes not well understood, it can be treated very effectively in the short term through a combination of prevention (learning what triggers the allergic reactions) and drug therapy.

Since the twentieth century, many mucosal inflammatory disorders have become dramatically more common; atopic eczema (AE) is a classic example of such a disease. It now affects 10-20% of children and 1-3% of adults in industrialized countries, and its prevalence there has more than doubled in the past thirty years.