When evaluating food allergy, it is very important to seek appropriate consultation with a trained and board certified Allergy and Immunology specialist. The first approach towards evaluating food allergy is to conduct a thorough medical history to determine: if food allergy is likely and what the most likely culprit food is.
A limitation in blood panel testings is the false positive results because of non specific antibody binding in the laboratory test. As a result, a patient might be told to avoid certain foods that he/she has been consuming without any problems. It is very important to understand that a positive IgE test towards a particular food does not necessarily diagnose food allergy towards the food. On the other hand, a person might be allergic towards a particular food and have negative blood test. As a result, it is not recommended that patients pursue broad screening panels to screen for food allergy without proper supervision by an Allergy & Immunology specialist.
There are instances when blood tests are appropriate. When a food allergy is appropriately diagnosed, blood tests can be done to monitor IgE levels of a specific food to determine if a person is “growing out” of the food allergy. Ultimately, an oral food challenge needs to be done to determine if the food allergy has been out grown.
Finally, there are tests being offered to diagnose food allergy by testing to IgG and IgG4. At present, these tests lack scientific evidence to support its use in the evaluation of food allergy.