Eczema is a general term for many types of skin inflammation (dermatitis). The most common form of eczema is atopic dermatitis (sometimes these two terms are used interchangeably). However, there are many different forms of eczema.

Eczema can affect people of any age, although the condition is most common in infants, and about 85% of those affected have an onset prior to 5 years of age. Eczema will permanently resolve by age 3 in about half of affected infants. In others, the condition tends to recur throughout life. People with eczema often have a family history of the condition or a family history of other allergic conditions, such as asthma or hay fever. The nature of the link between these conditions is inadequately understood. Up to 20% of children and 1%-2% of adults are believed to have eczema. Eczema is slightly more common in girls than in boys. It occurs in people of all races.

Eczema is not contagious, but since it is believed to be at least partially inherited, it is not uncommon to find members of the same family affected.