Sep 26 2016

Review Criticizes IgG Testing for Food Allergies

immunoglobulins-typesIf you have a child in school then you have probably already noticed how common perceived food allergies are. Every year we get a list of foods that are banned from the school because of reported allergies. Peanuts are the most common. This is a reasonable policy for the school as genuine food allergies can cause life-threatening anaphylactic reactions.

It has also been known for a long time that the number of people who perceive that they or their children have a food allergy (35%) is far greater than the number of people who have proven allergies (2-5%).

A recent review of the literature, published in the Canadian Medical Association Journal, takes aim at one factor contributing to this gap between public perception and medical reality – IgG antibody testing. 

Allergies and Antibodies

A allergic reaction is an immune reaction against a specific substance. There are essentially two types of allergies reactions, an immediate reaction caused by IgE antibodies, and a delayed reaction caused by IgG antibodies.

The IgE reaction is what we know as a true allergic reaction – an immediate redness, swelling, itching, watery eyes, and closing of the throat. If severe these are medical emergencies as they can be life threatening. This is why some people carry an epipen, to quickly reverse the symptoms of an acute allergic reaction.

IgG antibody mediated immune reactions are more complex. They can cause long term skin and GI symptoms. Celiac disease, an allergy to gluten, is an IgG reaction.

There is not a simple relationship between the presence of IgG to specific food proteins and adverse reactions, however. In some specific instances, like gluten sensitivity, there is an established relationship. However, in the case of most food proteins there is no relationship between IgG levels and any clinical outcome.

Further, IgG can actually be protective against IgE reactions. That is exactly what allergy desensitization is all about – exposing patients to small amounts of a substance to that they produce protective IgG antibodies to block the IgE reactions.

What this means is that IgG testing for food proteins does not (except for specific cases like Celiac) have clinical validity. In other words, if you test positive for IgG to a specific food that does not mean that the food is causing you any symptoms and it does not mean you will benefit in any way from avoiding that food.

Alternative Reality

The science-based standard of care is based on a genuine desire to help people by having a thorough understanding of the science and a thoughtful and evidence-based approach to specific interventions. In other words – we want to know that an intervention is actually helping. We also know how easy it is to be deceived that a treatment is helping you or your patient when it is, in fact, doing nothing or may even be harmful.

In the case of IgG testing, it has been thoroughly studied to ask all the relevant questions, and it has been found to be unhelpful in assessing food allergies in general.

The lead author of the current review is quoted as saying:

“Many guidelines, including Canadian guidelines, have said that this testing has no room in the diagnosis of food allergy or intolerance,” says Abrams, an immunologist with the University of Manitoba who specializes in pediatric allergies.

“If you’re looking specifically for food allergy, I think that the best guidance — or the optimal guidance —would come from somebody trained in allergies.”

There are several specific harms that are done by invalid IgG food testing. One is simply the wasted expense of the test. One popular IgG food screen is called Hemocode and costs $450.

Further, a false positive test can result in someone unnecessarily avoiding a specific food, which could compromise their nutrition. It can be challenging to eliminate common foods from your diet and can adversely affect quality of life. This burden also spreads to others, including an entire school if you believe your child to be allergic. Finally, a false negative test may cause someone to reintroduce a food to which they are genuinely allergic.

For all these reasons the medical community has stopped doing IgG testing for general food allergies as they are simply not a valid test. They rely first on skin testing, looking for a reaction to a small test dose placed under the skin.

Alternative practitioners, however, do not follow the science-based standard of care (if they did, they wouldn’t be “alternative”). It always amazes me that someone can think not following the best scientific evidence is somehow a good idea.

IgG food allergy testing is popular among alternative practitioners, especially naturopaths. They get to perform expensive testing, and then make a list of dietary change recommendations, which fits their philosophy. The actual scientific evidence does not seem to factor in.

Yet, naturopaths get to pretend they are being scientific. They are ordering scientific-sounding blood tests that can seem very specific to someone not familiar with the actual science.

Diagnosing fake ailments also feeds into treating with fake treatments. You could then give homeopathic treatments for the non-existent food allergies diagnosed with a bogus test. That is alternative medicine.


IgG testing for food allergies is not valid, outside of very specific known IgG mediated syndromes like Celiac disease. Do not buy home IgG food allergy testing kits, and do not trust practitioners who will do wide IgG screening tests and then tell you to avoid long lists of foods. They are not following the evidence.

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