I talked briefly before about the lack of testing for food intolerance so now let’s delve more deeply into this issue. More specifically, let’s take a look at the difference between the common IgE-mediated reactions that have long been recognized as “food allergy” and the non-IgE-mediated responses, where the mystery lies.
IgE-mediated reactions will typically be swift and are potentially life-threatening; this type is why your child can no longer bring peanut butter sandwiches to school. Think swelling mouth and lips, projectile vomiting, breathing problems, and anaphylaxis. When the offending food enters the body, there is a nearly immediate immune response that causes symptoms very quickly. Researchers have now found there is a less common type of allergic reaction known as non-IgE-mediated food allergy (NFA) in which symptoms can take hours or even days to erupt. NFA is also an immune system response and commonly results in gastrointestinal responses, but can show up in other ways such as in the skin. The challenge with non-IgE-mediated food allergy is that it is not yet understood and there is no test available for it as there is for IgE-mediated. The only diagnostic tool available is elimination and challenge; taking the suspected food out of the diet to see if symptoms disappear, then adding it back in and watching for a reaction. Hence, it is believed that there is an under-diagnosis and non-validation of the degree of seriousness of this type of food allergy. In some cases, these symptoms are thought of as “food intolerance” because the offending foods come up as non-reactive in the IgE-mediated skin tests. They key to discerning the difference between NFA and food intolerance is in the type of response. Non-IgE-mediated responses are related to the immune system and have somewhat similar reactions as IgE-mediated, while food intolerance responses do not involve the immune system and thus have different symptoms. For me, this information is validating and encouraging as for years doctors and allergists have told me I should eat the foods that make my eyes and face swell, cause a rash, and make my asthma flare because my skin test said I wasn’t allergic to them. I have been insisting my issues were much bigger than an upset stomach or a little bit of itching, but usually get a pat on the head and sent on my way. With the more recent understanding of non-IgE, I finally have the confirmation I needed that there’s more to this story, and it’s not all in my head. To learn more, check out these sites. http://apfed.org/drupal/drupal/sites/default/files/files/IgE%20vs%20nonIgE%20reactions.pdf http://www.ncbi.nlm.nih.gov/pubmed/18782024 http://www.rch.org.au/uploadedFiles/Main/Content/allergy/Non%20IgE%20Food%20Allergy.pdf
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