atopic dermatitis is generally easily diagnosed based on a physical exam and visual inspection of the skin by a physician or dermatologist. additionally the history given by the patient and contributory family history help to support the diagnosis. a doctor may ask about any history of similar rashes and other medical problems including hay fever (allergies) and asthma. while currently there may be no single specific laboratory test that says unequivocally "this is atopic dermatitis " a skin biopsy (a sample of a small piece of skin that is sent to the lab for examination under the microscope) may be helpful to establish the diagnosis in harder cases. additionally gentle skin swabs (long cotton tip applicator or q-tip) samples may be sent to the lab to exclude infections of the skin which may mimic atopic dermatitis. since itching tends to be the main common symptom of the disease for many patients it is not possible to say all itching is atopic dermatitis. itching may be seen in many other medical conditions that have nothing to do with eczema. each patient experiences a unique combination of symptoms and the symptoms and severity of the disease may vary over time. the doctor bases the diagnosis on the individual's symptoms and may need to see the patient several times to make an accurate diagnosis. it is important for the doctor 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 or allergist (allergy specialist) for further evaluation. a valuable diagnostic tool is a thorough medical history which provides important clues as to the possible causes of the patient's ailment. the doctor may ask about all of the following: a family history of allergic disease whether the patient also has diseases such as hay fever or asthma exposure to irritants sleep disturbances any foods that seem to be related to skin flares previous treatments for skin-related symptoms use of steroids and the effects of symptoms on schoolwork career or social life. sometimes it is necessary to do a biopsy of the skin or patch testing to determine if the skin's immune system overreacts to certain chemicals or preservatives in skin creams. a preliminary diagnosis of atopic dermatitis can be made if the patient has three or more characteristics from each of two categories: major features and minor features. some of these characteristics are listed in the box below. skin scratch/prick tests (which involve scratching or pricking the skin with a needle that contains a small amount of a suspected allergen) and blood tests for airborne allergens generally are not as useful in diagnosing atopic dermatitis as a medical history and careful observation of symptoms. however they may occasionally help the doctor rule out or confirm a specific allergen that might be considered important in the diagnosis. negative results on skin tests are reliable and may help rule out the possibility that certain substances are causing skin inflammation in the patient. however positive skin scratch/prick test results are difficult to interpret in people with atopic dermatitis and are often inaccurate. in some cases where the type of dermatitis is unclear blood tests to check the level of eosinophils (a type of white blood cell) or ige (an antibody whose levels are often high in atopic dermatitis) are helpful. major and minor features of atopic dermatitis major features itching characteristic rash in locations typical of the disease (arm folds and behind knees) chronic or repeatedly occurring symptoms personal or family history of atopic disorders (eczema hay fever asthma) some minor features early age of onset dry rough skin high levels of immunoglobulin e (ige) an antibody in the blood ichthyosis hyper linear palms keratosis pilaris hand or foot dermatitis cheilitis (dry or irritated lips) nipple eczema susceptibility to skin infection positive allergy skin tests
how is atopic dermatitis diagnosed?