What Is Atopic Dermatitis/Eczema?
The skin is an organ that can become diseased. One fairly common skin condition, especially in some infants and children, is atopic dermatitis, or eczema. Other forms of skin diseases include seborrheic eczema (cause unknown) and contact dermatitis (such as poison ivy or contact with detergents and chemicals). Atopic dermatitis is the most difficult to treat—but it can be controlled.
What Are Symptoms of Atopic Dermatitis?
In infants, atopic dermatitis appears as an itchy rash, called pruritus. It appears first as small white pimples with red centers over the infant’s cheeks, neck and scalp. The rash can also appear on the outside surfaces of the arms and legs.
In older children, the rash appears on the inner forearm, behind the knees, and opposite the elbows. Skin that is chronically covered with the rash over time will become dry, thickened and more brown in color. Some children get the rash on the eyelids, palms of the hand and soles of the feet.
Teenagers and young adults get the rash most often in the bend of the elbow, back of the knees, ankles and wrists, and on the face, neck, chest, and palms of the hands and soles of the feet.
In some people, inhaled substances (such as dust mites, animal allergens and pollen) can cause flare-ups of atopic dermatitis. A bacterial, fungal or viral infection also can cause a flare-up. Food allergies may trigger an episode in children, but rarely in adults.
Atopic dermatitis is not contagious. Sometimes, though, scratching can lead to a bacterial infection. A Staphylococcus aureus bacterial infection of an area covered by eczema can cause impetigo, a skin infection that is contagious. (Other causes of impetigo are infections following poison ivy or an allergy to soap or makeup.) Most often impetigo occurs on the face, especially around the mouth and nose. It begins with tiny blisters that burst and may ooze fluid, then become crusted.
How Is Atopic Dermatitis Diagnosed?
To diagnose atopic dermatitis, the doctor will take a careful medical history, looking especially at allergy among other family members. If food is the suspected cause of a child’s eczema, the doctor may delete milk, egg, peanut, or other suspected foods from the child’s diet to see if symptoms go away. If there is a history of atopic dermatitis among other family members, the doctor may suggest that solid foods be withheld from infants until they are at least six months old.
Skin testing can help confirm that a food allergy is triggering flare-ups. An extract of the suspected food substance is used to scratch or prick the skin. If the patient is allergic, the area becomes red and swollen. But some people may have a positive reaction to a food that is not causing the eczema.
Skin tests also can be difficult if the patient already has a rash. In such cases, a blood test such as the RAST (radioallergosorbent test) is used to detect food-specific antibodies in the blood. Another lab test analyzes a blood sample for the presence of eosinophils, cells that cause inflammation.
A food challenge can confirm that atopic dermatitis is triggered by food. Suspected foods are removed from the diet, then they are added back in, first in small amounts then in increasing quantities, and the patient is watched to see if symptoms recur.