"Atopic" refers to a group of conditions that can run in families and usually occur together. These include asthma, hay fever, and atopic dermatitis. This is known as the "atopic triad." Children who outgrow atopic dermatitis may later develop seasonal allergies or asthma. But atopic dermatitis does not cause asthma or allergies.

About 13 in 20 people with atopic dermatitis develop symptoms in the first year of life. Nearly 4 in 5 develop symptoms before the age of 5. Atopic dermatitis can clear up entirely by the time a child becomes an adult. But in about half of the cases, it continues into adulthood. It sometimes 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 gets worse, that period is called a flare (exacerbation). When it gets better or clears up entirely, that period is called a remission. In some people, this cycle of flares and remissions may be seasonal in very hot or very cold weather. A flare can be caused by an irritant or an allergen. The rash can appear on any part of the body. But where it shows up depends on your age.

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.

Certain triggers can make this condition worse. For example, stress, hot or cold temperature, dry conditions, certain fabrics, metals, or detergents can cause a flare-up.

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 is called lichenification. It can develop because of constant scratching and rubbing. Red, scaly skin can develop when the immune system in the skin becomes over-activated.

The outer layer of skin (epidermis) 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. It protects the inner layer from damage. The skin of a person with atopic dermatitis loses too much moisture. This reduces its protective abilities. It is more vulnerable to certain infections. People with eczema are more likely to have a severe and possibly life-threatening reaction to the smallpox vaccine. Those with eczema also can develop eczema herpeticum. This is a herpes infection in the skin that can be life-threatening.