"Atopic" refers to a group of conditions that run in families and usually occur together. People with atopic dermatitis also may suffer from asthma and/or allergies like hay fever. Children who outgrow atopic dermatitis may later develop seasonal allergies or asthma. Atopic dermatitis does not cause asthma or allergies, however.

Sixty-five percent of patients with atopic dermatitis develop symptoms in the first year of life, and 90 percent develop symptoms before the age of 5. Atopic dermatitis can go into permanent remission by the time a child reaches adulthood. In about 60 percent of cases, however, it continues into adulthood. Occasionally, it shows up for the first time later in life. In adults, atopic dermatitis can show up after the skin is exposed to harsh conditions.

When the condition worsens, that period is called a flare or exacerbation. When it improves or clears up entirely, that period is called a remission. In some people, this cycle of flares and remissions may be seasonal.

Eczema is a general term for many types of dermatitis (inflammation of the skin). Atopic dermatitis is the most common type of eczema. Acne is a different kind of skin disease; pimples are a symptom of acne. Like eczema, psoriasis is a chronic skin disease, but it is caused by a different disorder of the immune system.

Today, medical experts know stress can make the disease worse, but stress does not cause it. Atopic dermatitis appears to result from a combination of genetic and environmental factors. It is not contagious and can't be passed from one person to another.

Symptoms vary from person to person. Other symptoms include cracks behind the ears and a rash on the cheeks, arms and legs. Scratching and rubbing the skin make the condition worse. The other answers are symptoms for other types of eczema.

Thick, leathery skin, called lichenification, can develop because of constant scratching and rubbing. Red, scaling skin can develop when the immune system in the skin becomes over-activated.

The epidermis, or outer layer of skin, is divided into two parts. The inner part contains moist, living cells; the outer part contains dry, dead cells. For a person with normal skin, the outer part acts as a barrier, protecting the inner layer from damage. The skin of a person with atopic dermatitis loses too much moisture, reducing its protective abilities. People with eczema are more likely to have a severe and possibly life-threatening reaction to smallpox vaccination. Those with eczema also can develop eczema herpeticum, a herpes infection in the skin that can be life-threatening.