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Food has a social component that is integral to every culture and society on our planet. However, food can be foe as well as friend, food intolerances can negatively impact our quality of life and in the case of food allergies they can even be lethal. If we ask Google, from headaches to acne nearly every single ailment can be attributed to a food or diet and usually the cure is also attributed to a different food or diet.

The “free from” industry is booming, when I first moved to the city I currently live in if I wanted gluten free products I would have had to go to a pharmacy and, with luck, they would be in the corner collecting dust along with those weird herbal sweets your grandmother used to love. Fast forward two years and now entire sections of supermarkets are dedicated to gluten and lactose free products. This is obviously a great thing, especially for people with genuine diagnosed conditions such as celiac disease. The increased awareness of food related problems has led many of us to question “is this headache/lack of energy/lack of sleep caused by a food intolerance?”

There are plenty of people who will tell you the answer is yes and their advice usually comes with a large price tag. This article will explain to you why the IgG antibody food intolerance test is a waste of both time and money.

I want to make it very clear that although I will be mentioning food allergies this article is not about whether you should or shouldn’t test for a suspected food allergy. If you suspect that you may have a food allergy then go to your physician, and by that I mean a real doctor that works in a clinic or a hospital, not some charlatan on the internet with MD after their name. What I will be discussing in this article is the food intolerance blood tests that are advertised on the internet and in some pharmacies.

What Is the Test?

The test is pretty straight forward—you order a testing kit online from one of the labs offering the test. Once it arrives you take a blood sample and then send that blood sample back to the lab. The lab will test your blood for IgG antibodies that are specific to a wide range of foods, usually in the range of 200 different foods. What I mean by specific is that, for example if when they test your blood against a sample of chicken protein some of the IgG antibodies bind to that protein they are “specific” to that protein or food.

Once the lab has tested all the foods they will return a report to you with the results. Different labs may do it differently but the ones I have seen use a traffic light system. Red for foods with high amounts of IgG binding which should be avoided. Yellow for foods that are “borderline” and should only be eaten in moderation. Finally, green for foods that have little or no IgG which means you can eat them to your heart’s content.

So, what’s the problem?

It all sounds so simple, do the test and then avoid the red foods. However, there are two pretty large problems with this method of food intolerance testing. The first is related to the testing procedure, and the second is with the actual function of the IgG antibody.

True Food Intolerances

We’ll start with the method and we’ll assume that the IgG antibody is involved with food intolerances (that will be tackled in the next section). When I did my allergy certificate at university we were repeatedly told that the most important part of an allergy diagnosis was the patient history. Without a detailed patient history, the blood test results are at best unhelpful. The sole presence of antibodies is not sufficient enough to give a diagnosis, there has to be a history of symptoms in order to be certain that you are indeed allergic (or in this case intolerant) to a particular food.

Blood test results without patient history become unhelpful. As I said before both symptoms and the presence of antibodies are needed for a diagnosis. Just the presence of antibodies (with the absence of symptoms) to a particular food protein is known as sensitisation.1

When it comes to food allergies, if a person is sensitised to a food but does not have any allergic symptoms then the last thing they should do is stop eating that particular food. By ceasing to eat the food they are sensitized to could actually push the immune system away from tolerance towards allergy and the next time they encounter that food they could have a reaction.2 This is why in immunotherapy it is vitally important that the patient continues to eat the food they were allergic to even if (as is often the case) they do not like it. Coming back to food intolerance, just receiving a report of hundreds of foods, some of which you now have been told you cannot eat, is likely to lead to you following an unnecessarily restrictive diet resulting in increased risk of nutrient deficiencies and even worse, less gains in the gym.

The IgG Antibody

Before we get too in depth about antibodies I think it’s important to clarify what is allergy and what is intolerance because these words are often used interchangeably and causes confusion. Both allergy and intolerances are known as hypersensitivities which means they are reactions against something that a “normal” person would not react to. An allergy is a hypersensitive reaction that is driven by the immune system whereas an intolerance does not involve the immune system.3

A good comparison would be lactose intolerance and a true milk allergy. A person who is lactose intolerant does not produce any or insufficient amounts of the enzyme lactase which helps us digest the sugar lactose, so when they consume milk they cannot break down lactose and this causes digestive issues, these issues are not caused by the immune system. They can however consume lactose free milk. In the case of a milk allergic individual, their immune system has created antibodies against milk proteins so when they consume milk their immune system attacks it and the individual has the classic allergy symptoms, itchy rash, swelling, and difficulty breathing. A milk allergic individual could not consume lactose free milk because it still contains the milk proteins, however they could consume a hydrolysed or amino acid formula with lactose.

Moving on to antibodies, these are made by the B-cells of our adaptive immune system. Our immune system is made up of two parts, the innate and the adaptive. The innate is pretty basic in that it attacks anything that is not “us.” On the plus side it is very quick to respond. The adaptive immune system is a bit slower to respond but it has a “memory” so to speak, so the next time it encounters anything nasty it usually deals with it before we even notice we’re sick.

One of the chief weapons in the arsenal of the adaptive immune system is the antibody (or immunoglobulin), the B-cells make several different types of antibody each with a different role in the immune system. The most famous antibody is probably IgE. The original role of IgE was to deal with parasitic infections but it is more widely known as the antibody behind allergic reactions.4

When the B-cell makes an antibody they are “specific” to a particular protein (in the case of food allergy a food protein), when the antibody next encounters that protein they attach to it and drive an immune response. In the case of IgE they sit on top of certain immune cells (mast cells), and when they encounter the specific protein or antigen they bind to it and cause these cells to release histamine. It is this histamine that causes your typical allergic reactions and also why people with allergies usually carry antihistamines with them.

Moving on to the IgG antibody, there are actually four subclasses of IgG antibody, IgG1, IgG2 etc. each with a slightly different function. All the IgG subclasses are very good at enhancing a process called phagocytosis which involves certain cells of the immune system (macrophages) engulfing bacteria and destroying them. IgG1 for example is very good at a process known as ADCC (Antibody-Dependent Cell-mediated Cytotoxicity), here the IgG1 will attach to a target cell and immune cells will recognise that attachment as a signal that that particular cell needs to be destroyed.4

IgG Food Interolence Science

Proponents of the IgG food intolerance tests will point to the antibody’s ability to activate several cells of the immune system as “evidence” that the antibody can and does mediate non-allergic reactions to foods. However, when we examine the role of IgG4 we see that this is not the case. In 2012 researchers from Norway examined the link between IgG, IgG4 and IBS (irritable bowel syndrome). IBS is a condition related to food that has many of the symptoms of food intolerances, bloating, and change in bowel habits so there have been attempts to link the condition to IgG antibodies.5

In the Norwegian study they compared IgG and IgG4 food specific antibodies of IBS subjects and healthy symptom free subjects. Not only did the researchers find that the IBS group’s IgG and IgG4 antibodies did not match to their trigger foods (foods they know exacerbate their symptoms), but there were no differences in levels of IgG and IgG4 between the IBS and control group. What the researchers did find was that the higher levels of the antibodies matched foods that both groups ate regularly, in the case of the IBS group these were their “safe foods” and in the control group merely foods that they ate often.

The researchers concluded that it was unlikely that IgG and IgG4 antibodies played a role in IBS and that the presence of these antibodies merely reflected ones diet.6 In other words, the more you eat of something the more IgG specific to that food you have. In recent years it has become apparent that IgG, and in particular IgG4, is not just a reflection of a diet but a marker of tolerance and is protective against allergic reactions.

For non-allergic people we make IgG4 antibodies (as opposed to IgE) against proteins to mark them as “safe” and prevent any chance of an allergic reaction. This has been labeled an IgG4/IgE ratio. Non-allergic bee keepers have been shown to have an IgG4/IgE ratio 1000 times higher than individuals who are allergic to bee venom.7 During immunotherapy, allergic individuals gain tolerance not by reducing their numbers of IgE but by increasing their numbers of IgG1 and in particular IgG4. The IgG4 antibodies compete with the IgE antibodies and prevent them attaching to the mast cells and so prevent them from causing reactions.8

Proceed with Caution

When it comes to food proteins, the IgG antibody and in particular the IgG4 subclass appear to have anti-inflammatory effects that prevent allergic (and intolerance) reactions in both allergic and non-allergic individuals. To paraphrase EAACI (the European Academy of Allergy) the testing of IgG for food intolerances is “irrelevant” and should not be performed.9 The companies that continue to promote the IgG blood tests either do not fully understand the function of the IgG antibody or worse, they do and are continuing to sell their product anyway. I really hope it isn’t the latter. 


1. Van Ree. R et al. 2014. Allergic sensitization: host-immune factors. Clinical and Translational Allergy. 4:12.

2. James. LK et al. 2011. Long-term Tolerance After Allergen Immunotherapy is Accompanied by Selective Persistence of Blocking Antibodies. Journal of Allergy and Clinical Immunology. 127:509-516.

3. Johansson. SGO et al. 2004. Revised nomenclature for allergy for global use: Report of the Nomenclature Review Committee of the World Allergy Organization, October 2003. Journal of Allergy and Clinical Immunology. 133 (5): 832-836.

4. Owen. J et al. 2013. Kuby Immunology, 7th Edition. Macmillan.

5. Philpott. H et al. 2013. Alternative Investigations for Irritable Bowel Syndrome. Journal of Gastroenterology. 28: 73-77.

6. Ligaarden. S et al. 2012. IgG and IgG4 Antibodies in Subjects with IBS: A Case Control Study in the General Population. BMC Gastroenterology. 12:166.

7. Carballido. JM et al. 1993. T-cell Epitope Specificity in Human Allergic and Non-Allergic Subjects to Bee Venom Phospholipase A2. Journal of Immunology. 150:3582-3591

8. Bischoff SC & Sellge G. 2014. Food Allergy: Adverse Reactions to Foods and Food Additives, Fifth Edition. Chapter 2: The Immunological Basis of IgE-Mediated Reactions. John Wiley & Sons, Ltd.

9. Stapel. SO et al 2008. Testing for IgG4 Against Foods is Not Recommended as a Diagnostic Tool: EAACI Task Force Report. Allergy. 63: 793-796.

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