What is atopic dermatitis (eczema)?

Atopic dermatitis is a chronic (long-lasting) disease that affects the skin. The word "dermatitis" means inflammation of the skin. "Atopic" refers to a group of diseases that are hereditary (that is, run in families) and often occur together, including asthma, allergies such as hay fever, and atopic dermatitis. In atopic dermatitis, the skin becomes extremely itchy and inflamed, causing redness, swelling, cracking, weeping, crusting, and scaling. Atopic dermatitis most often affects infants and young children, but it can continue into adulthood or first show up later in life.

Flares and remissions

In most cases, there are periods of time when the disease is worse, called exacerbations or flares. These are followed by periods when the skin improves or clears up entirely, called remissions. Many children with atopic dermatitis will experience a permanent remission of the disease when they get older, although their skin often remains dry and easily irritated. Environmental factors can bring on symptoms of atopic dermatitis at any time in the lives of individuals who have inherited the atopic disease trait.

The most common type of eczema

Atopic dermatitis is often referred to as "eczema," which is a general term for the many types of dermatitis. Atopic dermatitis is the most common of the many types of eczema. Several have very similar symptoms. Atopic dermatitis is very common. It affects males and females equally and accounts for 10 to 20 percent of all referrals to dermatologists (doctors who specialize in the care and treatment of skin diseases).

Factors associated with occurrence

Atopic dermatitis occurs most often in infants and children and its onset decreases substantially with age. Scientists estimate that 65 percent of patients develop symptoms in the first year of life, and 90 percent develop symptoms before the age of 5. Onset after age 30 is less common and often occurs after exposure of skin to harsh conditions.

People who live in urban areas and in climates with low humidity seem to be at an increased risk for developing atopic dermatitis. Although it is difficult to identify exactly how many people are affected by atopic dermatitis, an estimated 10 percent of infants and young children experience symptoms of the disease. Roughly 60 percent of these infants continue to have one or more symptoms of atopic dermatitis into adulthood. This means that more than 15 million people in the United States have symptoms of the disease.

Heredity and environment

The cause of atopic dermatitis is not known, but the disease seems to result from a combination of genetic (hereditary) and environmental factors. Evidence suggests the disease is associated with other so-called atopic disorders such as hay fever and asthma, which many people with atopic dermatitis also have. In addition, many children who outgrow the symptoms of atopic dermatitis go on to develop hay fever or asthma. Although one disorder does not cause another, they may be related, thereby giving researchers clues to understanding atopic dermatitis. In the past, doctors thought that atopic dermatitis was caused by an emotional disorder. We now know that emotional factors, such as stress, can make the condition worse, but they do not cause the disease. Also, atopic dermatitis is not contagious; it cannot be passed from one person to another.

Types of eczema (dermatitis)

• 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 (dermatitis): 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: 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 common 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