Food allergies can cause flare-ups. Since an allergic reaction to food (either by skin contact during food preparation or by eating the food) can trigger an AD flare-up, it is important to identify the trigger foods. Diagnosing food allergies is extremely difficult. The surest way is to observe a worsening of eczema when a particular food is eaten. Sometimes this is only a coincidence with flaring and needs to be verified with a food challenge, where the suspected food is eaten in the doctor’s office. Withholding foods should be done only under the supervision of a physician, as serious nutritional damage can be caused by the elimination of foods suspected to cause flare-ups. Patients are seldom allergic to more than one or two foods.
A skin test, made by scratching the skin with the suspected allergen, is helpful if the test is negative (indication that the particular food will not affect the patient). If the scratched area becomes inflamed, the test is considered positive. But, unfortunately, positive results are difficult to interpret and are accurate only about 20 percent of the time. At best, positive tests provide a clue to a possible allergy but should not be accepted as the last word. Additionally, because the skin of AD sufferers is so sensitive, simply scratching it can cause inflammation, making the likelihood of a false positive skin test even higher. A blood test is another type of test to detect food allergies. Blood tests also have a very high rate of false positives and may be expensive.