Tuesday, November 15, 2011

What Type of Allergy Test Did You Have?

If you see a doctor about being tested for allergies, you are likely being tested for IgE (immunoglobulin E) antibodies. IgE antibody production "occurs right after ingestion or inhalation of an allergen and is referred to as a Type I immediate hypersensitivity reaction."1 This is the kind of allergy that can be life threatening and often requires EpiPens to be carried at all times. An IgE response is considered to be a 'true' allergy.

However, there is another type of allergy test that looks for a different kind of antibody, IgG (immunoglobulin G), and this test may or may not be offered by your doctor. IgG antibodies "are produced for several hours or days after exposure to an allergen and are called Type III delayed hypersensitivity reactions."2 Due to the delay in reaction time - sometimes up to three days - this type of allergy or 'sensitivity' is particularly difficult to connect to specific foods without first having an IgG test done or completing a very diligent elimination diet.


There is some controversy over IgG tests because the results are not always accurate. If a specific food has not been consumed within three weeks of testing, the body may not have produced sufficient IgG antibodies for the test to pick it up, causing a false negative. Some proteins are so similar (bananas and pineapple) that a person might test positive for both even if they are not allergic to both. This is considered a false positive. Due to these "inaccuracies" this test is often not offered when you request allergy testing from your doctor.

Despite the flaws of the IgG test, it does provide useful information. Results showing antibodies to a large percentage of the foods tested strongly indicates the presence of a leaky gut, or perforations in the intestinal lining that is allowing food proteins to enter into the blood stream. Results that you feel uncertain about can be challenged by proceeding with an elimination diet and then gradually reintroducing the suspected allergen over three days and noting any symptoms.

If you're sure that a certain food is causing your symptoms, but your results come back negative for IgE antibodies, you may also want to consider being tested for an IgG antibodies. It is quite possible for test results to come back negative for an IgE test, but positive for an IgG test and vice versa because they are testing for different antibodies.

If you're having allergy testing done, be sure to understand which type of test is being performed so that you're getting the complete picture.

Sources:
1, 2 http://www.rmalab.com/index.php?id=18

4 comments:

realfoodforager said...

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http://realfoodforager.com/2011/11/fat-tuesday-november-15-2011/

itchylittleworld said...

Our son tested negative to blood and skin prick tests, yet many foods cause immediate itching, hives, etc. Even the IgG test is not always accurate, like you mention. We did an elimination diet to determine the full list of foods he'd need to avoid. It was hard, but so worth it in the end.

Shanon Hilton said...

Good for you for doing the elimination diet! It takes a lot of dedication! Thanks for sharing!

Rae of Sunshine said...

I second doing an elimination diet for allergies. I had a sinus infection/heachache (sinusitis) for 7 years, and finally went to a ears, nose and throat specialist, only for him to tell me that I'm just sensitive and I'll have to live with it. Turns out it was caused by fungi (mushrooms and roasted peanuts). To that I just throw my hands up in the air. Not so special are you now specialist.