Each person experiences a unique combination of symptoms, which may vary in severity over time. The doctor will base a diagnosis on the symptoms the patient experiences and may need to see the patient several times to make an accurate diagnosis and to rule out other diseases and conditions that might cause skin irritation.

In some cases, the family doctor or pediatrician may refer the patient to a dermatologist (doctor specializing in skin disorders) or allergist (allergy specialist) for further evaluation.

A medical history may help the doctor better understand the nature of a patient’s symptoms, when they occur, and their possible causes. The doctor may ask about family history of allergic disease; whether the patient also has diseases such as hay fever or asthma; and about exposure to irritants, sleep disturbances, any foods that seem to be related to skin flares, previous treatments for skin-related symptoms, and use of steroids or other medications. A preliminary diagnosis of atopic dermatitis can be made if the patient has three or more features from each of two categories: major features and minor features. Some of these features are listed here.

Currently, there is no single test to diagnose atopic dermatitis. However, there are some tests that can give the doctor an indication of allergic sensitivity.

Pricking the skin with a needle that contains a small amount of a suspected allergen may be helpful in identifying factors that trigger flares of atopic dermatitis.

Negative results on skin tests may help rule out the possibility that certain substances cause skin inflammation. Positive skin prick test results are difficult to interpret in people with atopic dermatitis because the skin is very sensitive to many substances, and there can be many positive test sites that are not meaningful to a person’s disease at the time. Positive results simply indicate that the individual has IgE (allergic) antibodies to the substance tested. IgE (immunoglobulin E) controls the immune system’s allergic response and is often high in atopic dermatitis.

Recently, it was shown that if the quantity of IgE antibodies to a food in the blood is above a certain level, it is diagnostic of a food allergy. If the level of IgE to a specific food does not exceed the level needed for diagnosis but a food allergy is suspected, a person might be asked to record everything eaten and note any reactions. Physician-supervised food challenges (that is, the introduction of a food) following a period of food elimination may be necessary to determine if symptomatic food allergy is present. Identifying the food allergen may be difficult when a person is also being exposed to other possible allergens at the same time or symptoms may be triggered by other factors, such as infection, heat, and humidity.