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A Blood Test for Food Allergies Can Clarify Your Eating Strategies!
Is there a blood test for food allergies? Actually, there is more than one blood test for food allergies. The radioallergosorbent test, or RAST, measures the amount of IgE (the antibody involved in classical allergic responses) in a person’s blood in response to a specific allergen. This test has been replaced in the last 10 to 20 years by the IgE-specific immunoassay, a test that is similar, but eliminates the radioactive part of the older test. Many doctors call this newer test the RAST, though. It’s sure a lot easier to say. If you’d like to read a really involved description of how this test works, check out the Wikipedia article. People with IgE-type, or “classical,” allergies usually show symptoms within a short time after taking in the food they’re allergic to. The RAST-type tests will usually show clearly which foods a person has classical allergic responses to—that is, hives, rhinitis (nasal allergies), eczema, or asthma. This is especially helpful if you are in danger of a sudden, severe reaction, and might need to keep an Epi-pen with you at all times. The problem is that not all allergies involve IgE, the antibody tested in the RAST. So, if you get diarrhea from eating wheat, you may still test negative for a wheat allergy. This is why many doctors would say that your allergy is not a “true” allergy, but an “intolerance”—because it doesn’t show up on their tests. Don’t let this make you feel as if your condition is somehow “less real” because doctors don’t call it a “true allergy.” This is just the way they’ve chosen to define their terms. But if you’re are being treated as if you don’t have a real, treatable medical condition, then you should find a new doctor. See my treatment page for ideas on finding one. Another blood test for food allergies is the ELISA. This is a test that has a lot of applications, and one of them is finding delayed food allergies. The ELISA delayed food allergy test deals mostly with IgG, another type of immunoglobulin. Since people with food “intolerances” often do not react for many hours after eating a problem food (as in the wheat example above), this type of test is indispensable. Many people with conditions like irritable bowel have found answers through taking this test. But, again, this test is focusing on one type of immunoglobulin, and it’s possible for the results to be misleading. After having a blood test for food allergies (or both of them), it may be a good idea to use an elimination diet and a food/symptom diary to help you know which other foods may be problems for you. You might do this by:
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