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Atopic dermatitis is a chronic (long-lasting) disease that affects the skin. It cannot be passed from one person to another. The word "dermatitis" means inflammation of the skin. "Atopic" refers to a group of diseases where there is often an inherited tendency to develop other allergic conditions, such as asthma and hay fever.
Atopic dermatitis is often referred to as "eczema," which is a general term for the several types of inflammation of the skin. Atopic dermatitis is the most common of the many types of eczema. It affects males and females and accounts for 10 to 20 percent of all visits to dermatologists. More than 15 million people in the United States have symptoms of the disease.
Symptoms vary from person to person. The most common symptoms are dry, itchy skin and rashes on the face, inside the elbows and behind the knees, and on the hands and feet. Itching is the most important symptom of atopic dermatitis. Scratching and rubbing in response to itching irritates the skin, increases inflammation, and actually increases itchiness. Itching is a particular problem during sleep when conscious control of scratching is lost.
The appearance of the skin that is affected by atopic dermatitis depends on the amount of scratching and the presence of secondary skin infections. The skin may be red and scaly, be thick and leathery, contain small raised bumps, or leak fluid and become crusty and infected.
Atopic dermatitis may also affect the skin around the eyes, the eyelids, and the eyebrows and lashes. Scratching and rubbing the eye area can cause the skin to redden and swell. Some people with atopic dermatitis develop an extra fold of skin under their eyes. Patchy loss of eyebrows and eyelashes may also result from scratching or rubbing.
Researchers have noted differences in the skin of people with atopic dermatitis that may contribute to the symptoms of the disease. The outer layer of skin, called the epidermis, is divided into two parts: an inner part containing moist, living cells, and an outer part, known as the horny layer or stratum corneum, containing dry, flattened, dead cells. Under normal conditions the stratum corneum acts as a barrier, keeping the rest of the skin from drying out and protecting other layers of skin from damage caused by irritants and infections. When this barrier is damaged, irritants act more intensely on the skin.
The skin of a person with atopic dermatitis loses moisture from the epidermal layer, allowing the skin to become very dry and reducing its protective abilities. Thus, when combined with the abnormal skin immune system, the person's skin is more likely to become infected by bacteria (for example, Staphylo-coccus and Streptococcus) or viruses, such as those that cause warts and cold sores.
Atopic dermatitis usually begins in childhood. As some children with atopic dermatitis grow older, their skin disease improves or disappears altogether, although their skin often remains dry and easily irritated. In others, atopic dermatitis continues to be a significant problem in adulthood.
The cause of atopic dermatitis is not known, but the disease seems to result from a combination of genetic (hereditary) and environmental factors.
Children are more likely to develop this disorder if one or both parents have had it or have had allergic conditions like asthma or hay fever. While some people outgrow skin symptoms, approximately three-fourths of children with atopic dermatitis go on to develop hay fever or asthma. Environmental factors can bring on symptoms of atopic dermatitis at any time in individuals who have inherited the atopic disease trait.
Atopic dermatitis is also associated with malfunction of the body's immune system. Scientists have found that people with atopic dermatitis have a low level of a cytokine (a protein) that is essential to the healthy function of the body's immune system and a high level of other cytokines that lead to allergic reactions. The immune system can become misguided and create inflammation in the skin even in the absence of a major infection. This can be viewed as a form of autoimmunity, where a body reacts against its own tissues.
Things That Make Atopic Dermatitis Worse
Irritants and allergens can make atopic dermatitis worse. Irritants are things that may cause the skin to be red and itchy or to burn. They include:
Allergens are allergy-causing substances from foods, plants, animals, or the air. Common allergens are:
Stress, anger, and frustration can make atopic dermatitis worse, but they haven’t been shown to cause it. Skin infections, temperature, and climate can also lead to skin flares. Other things that can lead to flares are: