Food Allergies - Exams and Tests

Exams and Tests

To diagnose a food allergy, your doctor will start with a medical history and a physical exam. Your doctor will ask detailed questions about your symptoms and how soon they begin after you eat a suspected food. It is important to determine whether you have a food allergy or food intolerance. Your doctor may ask you to keep a record of all the foods you eat and any reactions.

Your doctor may ask you to try an elimination diet, an oral food allergy challenge, or both.

• In an elimination diet, you do not eat groups of foods that likely cause allergic reactions or specific foods based on your history and other tests. If the symptoms go away when you do not eat the food, the food is suspect. If the symptoms come back when you eat the food again, it may confirm that the food is causing the allergy. The diet usually lasts for 10 to 14 days.
• In an oral food allergy challenge, you eat increasing amounts of both suspect and nonsuspect foods while being observed. Your doctor watches to see if and when a reaction occurs. If you have reactions only to the suspect foods and not to the others, the diagnosis can be confirmed. This test usually is the best way to determine whether a food allergy exists.

You may also have allergy tests. These include:

• Skin tests. A liquid containing an allergen is put on the top layer of skin, and the skin is pricked. If the skin reacts with a raised itchy area (called a wheal), it usually means that you are allergic to that allergen. Skin tests are quick, simple, and relatively safe, but results can be false-positive, meaning that even though your skin reacts to the food, you are able to eat it without symptoms. If you are extremely allergic, skin testing may be dangerous.
• Enzyme-linked immunosorbent assay (ELISA).. A blood sample is taken from a vein and tested for immunoglobulin E (IgE) antibodies, which are produced in response to particular allergens.

Food allergy tests that are not helpful or are unproven include:³

• IgG4 antibody.
• Provocation/neutralization.
• Cytotoxicity.
• Applied kinesiology.