To Test or Not to Test: What is the Deal With Food Allergy Testing?

One of the most common questions allergists hear from families is, “Can we do an allergy test just to make sure?” Parents often ask for allergy testing when a child has ongoing symptoms such as rashes, abdominal pain, behavioral changes or headaches.

To understand when testing is helpful, it is important to know the difference between food allergies, food intolerances and food sensitivities.

• A food allergy is a reaction caused by an immune reaction to a food. Most reactions are IgE mediated and often causing hives, vomiting, swelling, cough or runny nose. It is very uncommon for someone to have a food allergy to a food they have eaten many times.
• Food intolerances occur when the body has trouble digesting specific food and can typically cause abdominal symptoms such as bloating, diarrhea or abdominal pain.
• Food sensitivities are less understood and refer to the possibility of a food causing inflammation in the body. Food sensitivities are possible in people who have a pro-inflammatory condition such as a diagnosed auto immune disease.

Currently, reliable testing only exists for IgE-mediated food allergies. IgE is Immunoglobulin E, a type of antibody produced by the immune system that acts as an allergy-specific marker in the blood. There is no testing for non-IgE mediated food allergies, food intolerances or food sensitivities. For IgE food allergies, testing has a high rate of false positives. A positive food allergy test simply means someone may be allergic and further testing is needed. Because of this, allergy testing is recommended when a child’s history suggests an IgE mediated food allergy or to see if the child has outgrown their food allergy. The lack of testing can be frustrating for families hoping for ways to manage their child’s symptoms. So, how do allergists confirm an allergy?

• The oral food challenge is the most commonly used test which involves feeding the suspected food and observing for a reaction
• A skin test can be performed in an office with immediate result. The test involves a needless prick to the skin to with the allergen and a control to determine if there is an allergic reaction.
• A blood test measures the allergy cell, or IgE. Blood tests can be unreliable and show up as false positives.
• Allergy component testing focuses on the part of the food that may cause the allergy, but often still requires a food challenge to confirm the allergy.

It is important to pay attention to your child’s history with allergies and symptoms of an allergic reaction and have a conversation about it with your allergist. If the tests come back positive, it is important to remember that there may not be an allergy and the results cannot determine how severe a reaction will be. Speaking with your child’s allergist about their reactions with food is the best way to figure out your child’s allergy.