Dermatitis, atopic: A skin disease characterized by areas of severe itching, redness, scaling, and evidence of scratching (excoriation). When the eruption (rash) has been present for a prolonged time, chronic changes occur due to the constant scratching and rubbing known as lichenification (thickening of the skin with accentuation of the skin lines to form a crisscross pattern).
This disorder usually affects young children on the face and extensor surfaces of the arms and legs (elbow and knee sides). Older children and adults are usually affected on the sides of the neck and on the palms and soles.
Atopic dermatitis is frequently associated with other atopic (allergic) disorders, especially asthma and allergic rhinitis (hay fever). A defect of the immune system within the skin has been shown, but the reason for this is unknown.