Choices for health can be complicated – especially when you have health care practitioners with different opinions and/or the information available is contradictory. This is why it is important for us as consumers to do our research and make informed decisions for ourselves.

Such is the case with food sensitivity testing which has become a popular diagnosis tool in the natural health community. Different from ‘skin prick’ allergy tests which measure the IgE antibody reaction and produce almost immediate results, food sensitivity testing standardly measures the IgG antibody reaction to up to 96 different foods via a blood sample.

While IgE allergy testing is supported by significant scientific research, IgG testing is not recognized by the allopathic community due to its lack of evidence-based research. Clinical trials on IgG testing have by large shown inconsistencies¹; however, there are many published clinical trials demonstrating positive results with food elimination diets based on IgG testing, particularly for irritable bowel syndrome.^2,3,4

It is a tricky subject, so with this article, we hope to help you better understand the difference between the two tests and provide insights to both sides.

First of all, let’s clarify the difference between food intolerance/sensitivity and allergy. While the former terms are usually used interchangeably, their symptoms differ from allergies in that they are milder, may show up hours or days after consumption, and are normally related to the gut. Food allergies are immediate and can be severe.⁵

What is the difference between an IgE and IgG?

IgE antibodies are found in the lungs, skin and mucous membranes and cause the body to react against foreign substances such as pollen, fungus spores, and foods to which we are allergic. The response to “invaders” that have entered the body is almost immediate and produces symptoms like runny nose, sneezing, difficulty breathing, swelling, and hives. In even more serious cases IgE reactions can lead to anaphylactic shock (as in extreme peanut allergies). Symptoms are treated with medications that block the release of histamines.

IgG (Immunoglobulin G) antibodies are found in all body fluids and are very important in fighting bacterial and viral infections. These antibodies provide long-term resistance to infections and produce what are referred to as delayed food allergies. Symptoms, ranging from inflammation, bloating, indigestion, headache, foggy brain and nausea, may occur hours or even days after the offending food has been ingested. The degree and severity of symptoms vary based on the genetic makeup of the individual.

According to many natural health care practitioners, digestive problems play a major role in the development of IgG food allergies. Some individuals have leaky gut, enabling food particles to enter the bloodstream. When these particles are recognized by the immune system, the body has an immune response and more antibodies are created to fight the perceived infection, which can lead to a weakening of the overworked immune system. IgG food sensitivities are treated by removing problem foods from the diet and by helping digestion with probiotics and other healing nutrients.

“There is not great research to support IgG testing for food sensitivity,” says Heather Zwickey, Ph.D., dean of the School of Research & Graduate Studies at the National College of Natural Medicine and director of NCNM’s Helfgott Research Institute. Zwickey explains that while IgG1, IgG2, and IgG3 may be related to food hypersensitivity, IgG4 could be due to repeated exposure to a food, and unfortunately, the vast majority of food sensitivity tests do not discriminate between IgG types. Therefore, their tests are uninterpretable. “The IgG4 antibody is a conundrum; it can be made to a food to which someone is allergic, or a food that is eaten often.” She adds that in order to know which it is, the food has to be eliminated (for at least 50 days), and then if IgG4 shows up, it is not due to repeated exposure.

Local naturopathic doctor Shannon Sinsheimer agrees that the reason over consumption of food causes an intolerance is typically due to digestive issues or leaky gut disorder. “When a food is not properly broken down, or the GI is not functioning properly, food sensitivities develop whether they are common dietary choices or not.”

We first mentioned food intolerance testing in last issue’s “Frog in My Throat” article regarding excessive phlegm production. I did IgG food intolerance testing to see if specific foods were a core cause. Following are my results and analysis.

My tests showed highest intolerance to dairy products, lima beans, eggs, and almonds. I had given up dairy a year prior, so I considered these intolerance foods that I shouldn’t be eating (since it certainly was not due to overconsumption). I rarely ate lima beans so they fit in that category as well. Almonds I contributed to overconsumption as I was now drinking almond milk and eating handfuls of these healthy nuts every day. I cut back switching to coconut milk and mixed nuts. I considered eggs the culprit food. I didn’t eat large quantities because they tended to give me slight indigestion, so based on my body’s reaction and these test results, I took a break and symptoms diminished.

“In my opinion, the most important aspect of understanding these tests is that they are rough guides that we use with the clinical and symptomatic picture to advise on dietary recommendations to alleviate disease,” says Dr. Sinsheimer. She adds that food intolerance testing is not black and white, but rather an aid in identifying the probable cause, or foods that may be aggravating your system. “IgG testing is a clinical tool that gives me exceptional insight, but I also realize its limitations mean that I still have to use my critical thinking skills to apply the results to each individual as I see appropriate and beneficial.”

I found the test beneficial and have made diet modifications which have helped my condition. While others I know have done the same for various health concerns, it is beneficial to consider the facts when making lifestyle alterations. Knowledge is power, but when it comes to food sensitivities, listening to your body is a very good place to start.

References: 1) Science-Based Medicine. IgG Food Intolerance Tests: What does the science say? Scott Gavura February 2, 2012 http://www.sciencebasedmedicine.org/igg-food-intolerance-tests-what-does-the-science-say; 2) Food elimination based on IgG antibodies in irritable bowel syndrome: a randomised controlled trial.Atkinson W1, Sheldon TA, Shaath N, Whorwell PJ. 2004 Oct;53 (10):1459-64; 3) The value of eliminating foods according to food-specific immunoglobulin G antibodies in irritable bowel syndrome with diarrhoea. Guo H1, Jiang T, Wang J, Chang Y, Guo H, Zhang W. J Int Med Res. 2012;40(1):204-10.; 4) Treating irritable bowel syndrome with a food elimination diet followed by food challenge and probiotics. Drisko J1, Bischoff B, Hall M, McCallum R. J Am Coll Nutr. 2006 Dec;25(6):514-22.; 5) Mayo Clinic Expert Answers: What’s the difference between a food intolerance and food allergy? James T C Li, M.D., Ph.D.