Many Neocate parents know that using allergy testing to determine food allergies can be tricky, because many children experience what may be considered a food intolerance or sensitivity, versus a true food allergy.
Generally, a food allergy is considered to be an immunoglobulin E (IgE) mediated immune response. (1) In a previous blog, we have outlined the standard tests that may be done to determine whether your child has an Ig-E mediated food allergy, such as a skin prick test or a RAST.
However, you or your child may have a negative IgE test, but still appear to have symptoms that are typical of a food intolerance or sensitivity. Several tests are now marketed as tools for determining these types of non-IgE mediated food reactions. While more research is needed to determine the accuracy of these tests, they may provide helpful clues as to which foods to consider eliminating from the diet. Some of these tests include:
Enzyme Linked Immunosorbent Assay (ELISA): A blood test that is intended to measure levels of immunoglubulin G (IgG) in response to different foods. However, elevated IgG does not always indicate an adverse food reaction. In fact, sometimes elevated IgG is an indicator that an IgE response, or a true allergy, has been successfully treated. This test may be helpful in providing clues as to which foods to consider eliminating, but remember that elevated IgG does not always mean that there is a negative reaction to the food. (2, 3)
Mediator Release Testing (MRT): A blood test that in intended to measure many types of non-Ig-E mediated food intolerances or sensitivities, including IgG response. Proponents of MRT believe that because it assesses multiple immune pathways it provides a more complete picture of which foods are causing symptoms compared to IgG testing. (3)
Atopy Patch Testing (APT): A skin test used to determine delayed food reactions. A preparation of the food is placed in an aluminum chamber on the skin for 48 hours. Twenty four hours after removal the skin is inspected for a reaction; a positive reaction is determined based on the level of redness and swelling. (1) Some practitioners find that APT is a great tool to use along side IgE testing in order to a get a more complete picture of all the foods that may be causing symptoms for you or your little one.
Have you tried any of these tests? We would love to hear about your experience!
References:
1. Carney, Liesje Nieman. (2009, July). Pediatric Food Allergies. Today’s Dietitian, 11, 48.
2. Joneja, Janice Vickerstaff. (2008, January). Food Allergies: Type II, III, and IV Hypersensitivities. Today’s Dietitian, 10, 10.
3. Keller, Maura. (2010, August). Get Certified- Provide a Valuable Service By Adding Allergy Testing to Your Practice. Today’s Dietitian, 12, 18.
