The American Academy of Allergy, Asthma and Immunology (AAAAI) has just released guidelines for diagnosing and managing food allergies. These guidelines were conceived because of a lack of uniformity among physicians in testing and treating food allergy.
Frequently, pediatricians, family physicians and internists will order tests for food allergy. It is especially important that non-allergist physicians – as well as allergists – have a standard guideline for handling food allergy issues.
The AAAAI starts by pointing out that food allergy is common, but that many persons also have adverse reactions to foods that are non-allergic in origin. Proper testing/evaluation can separate these disparate conditions.
The AAAAI notes that the most common food allergens are milk, eggs, peanuts, tree nuts, shellfish, wheat and soy. The natural tendency is for an individual to outgrow the allergy. This is true for most foods, and studies have found that 80 percent of children outgrow their food allergies. This, however, is not true for peanut, tree nut and shellfish, where statistics show that only 20 percent of children outgrow these allergies.
The AAAAI makes a strong point that a positive test does not necessarily mean the patient has a true allergy to the food. What is also needed is a relevant history of prior reaction to the tested food or a confirmation of the test by an oral challenge. Oral challenges can be done at home following an elimination period. In cases of severe anaphylactic food allergies, food challenges may be done in an allergist’s office or in a hospital.
The most sensitive mechanism for testing is skin testing which measures IgE levels to the food. The RAST test, ELISA or Immunocap are blood tests for IgE.
Some labs offer a non-standard IgG food test which has no relevant value in diagnosing food allergy.