Eczema: A particular type of inflammatory reaction of the skin in which there are typically vesicles (tiny blister-like raised areas) in the first stage followed by erythema (reddening), edema (swelling), papules (bumps), and crusting of the skin followed, finally, by lichenification (thickening) and scaling of the skin. Eczema characteristically causes itching and burning of the skin.

Eczema, which is also called atopic dermatitis, is a very common skin problem. It may start in infancy, later in childhood, or in adulthood. Once it gets underway, it tends not to go quickly away.

There are numerous types of eczema, including:

• Atopic dermatitis -- a chronic skin disease characterized by itchy, inflamed skin
• Contact eczema -- a localized reaction that includes redness, itching, and burning where the skin has come into contact with an allergen (an allergy-causing substance) or with an irritant such as an acid, a cleaning agent, or other chemical
• Allergic contact eczema -- a red, itchy, weepy reaction where the skin has come into contact with a substance that the immune system recognizes as foreign, such as poison ivy or certain preservatives in creams and lotions
• Seborrheic eczema -- a form of skin inflammation of unknown cause that presents as yellowish, oily, scaly patches of skin on the scalp, face, and occasionally other parts of the body
• Nummular eczema -- coin-shaped patches of irritated skin—most commonly on the arms, back, buttocks, and lower legs—that may be crusted, scaling, and extremely itchy
• Neurodermatitis -- scaly patches of skin on the head, lower legs, wrists, or forearms caused by a localized itch (such as an insect bite) that becomes intensely irritated when scratched
• Stasis dermatitis -- a skin irritation on the lower legs, generally related to circulatory problems
• Dyshidrotic eczema -- irritation of the skin on the palms of hands and soles of the feet characterized by clear, deep blisters that itch and burn.

For a comprehensive article on all kinds of eczema, including the diagnosis and treatment, please see Atopic Dermatitis (Eczema).