Atopic dermatitis (AD), also called atopic eczema, is a chronic allergic skin disease that usually occurs in people who have an atopy.

These people may develop any or all of three closely linked allergic conditions: atopic dermatitis, asthma, and hay fever (allergic rhinitis). Atopic conditions have a genetic predisposition and, therefore, usually run within families. However, up to 30 percent of AD sufferers have no identifiable family history of atopic disease.

People with AD have a functional defect in their skin which prevents it from staying moist. Their skin is dry, itchy and easily irritated.

Scratching dry and itchy skin causes a rash, leading to more irritation, itchiness and, ultimately, more scratching. The inflamed skin allows irritants, allergens, bacteria and viruses to easily enter, causing even further inflammation. Food allergens and inhaled allergens, particularly dust mites and animal dander, can also aggravate AD.

Atopic dermatitis usually begins during the first year of life and always within the first five years. It is often at its worst between the ages of two and four. However, AD generally improves after 2-4 years of age and may clear altogether by the teens.

In babies, the rash usually starts on the face or over the elbows and knees, which are easy to scratch and rub. It may spread to involve all areas of the body. Later in childhood, the rash typically settles in the elbows and knee folds. Other common areas for rashes include the hands, feet, scalp or behind the ears.

The most important prevention and treatment for dry skin is to "soak and seal" water in the skin daily. After soaking in a bath, pat dry and immediately apply a thick layer of moisturizer, such as petroleum jelly or cream, to seal in the water. Chemicals, solvents, soaps, detergents, fragrances and many synthetic fabrics are irritants and should be avoided. Cotton is best for all seasons, especially summer. For cool weather, layering is a great idea.

Low humidity, high humidity and sweating can dry and irritate the skin. Therefore, avoid overheating the home. Since children with eczema are often prone other allergies, keep family pets outdoors or at least off beds or sofas. Control dust mites with coverings for pillows and mattresses and frequently wash bedclothes in hot water.

Antihistamines such as Benadryl, provided particularly at night, are crucial to controlling itching. Topical steroids may be used to calm the inflamed skin. Other special topical creams such as pimecrolimus cream or tacrolimus ointment also treat inflammation, but do not cause steroid side effects. It is also important to treat infection early with antibiotics. In rare but severe cases, immunosuppressive agents such as cyclosporin, methotrexate or azathioprine, may be indicated. The latest treatments for atopic dermatitis will be discussed in my next column.

— Dr. Yong H. Tsai is board-certified in rheumatology, allergy and clinical immunology and has been practicing in this area since 1993. His website is