Food intolerance (or sensitivity) testing has become popular amongst alternative practitioners and consumers alike. In a world where we have unlimited access to information, education, and opinion (some valid others not so) it is of course expected that there is a growing awareness of symptoms and ailments that may be connected to the food we consume. This is at the forefront of the publicly facing gut-health movement.

There is no doubt that as consumers, we are more in tune with our bodies, with much of the population now having an increased perception of the various gastrointestinal, dermatological, and metabolism issues that in the past, were likely to have gone undiagnosed or simply overlooked by general practitioners. 

Enter food sensitivity testing. Essentially, where traditional medicine may fail to find an allergy or unable to identify a problem, alternative practitioners and holistic health companies offer a highly targeted and personalised answer to the desperate consumer. 

Not to be confused with allergy testing, Immunoglobulin G (IgG) food sensitivity testing proposes to link an immune response to foods or components of foods that are not well tolerated. These tests are abundant in the market. A quick web search reveals a host of professional clinics and practitioners offering testing, easily accessible to the consumer.

They are marketed as being able to identify the specific foods responsible for fatigue, acne, joint pain, eczema, gut malabsorption, and other chronic conditions like IBS, migraines, chronic inflammation, and more.

How does the test work? 

The testing is conducted by a blood sample that is exposed to a panel of foods. What is being tested is the reaction, specifically the binding of the IgG antibody to components of commonly consumed foods. This IgG antibody is a food-specific antibody that shows a physiologic response of the immune system to exposure to food (1). It is proposed that the degree of IgG binding to each food or component determines the degree of intolerance to the food (1).

Does the test actually work?

Well, yes and no. The test accurately and reproducibly determines the degree of antibody present in reaction to particular food components. But that doesn’t mean it indicates a sensitivity to a particular food. Clinical immunologists understand that the presence of IgG is a marker of simple exposure to the food, and even a tolerance to it (2,3,4). That means, that the degree of antibody present, simply demonstrates that there has been recent ingestion of the food and not that the body is not sensitive towards it at all. 

Ask anyone who has taken one of these tests and they are likely to rattle off a laundry list of both oddly specific and ubiquitous foods they are meant to avoid. On completing the test, a patient is usually presented with a multipage document of itemised foods by category and their degree of sensitivity. For example, a report may indicate that under the category of “dairy” specific cheeses such as cheddar or cottage cheese are the cause of the reaction. This is contrary to the current understanding of food allergy where the known allergenic component in the food type is identified. For example, β-lactoglobulin in dairy milk, not a specific type of cheese made by milk (1).

In short, there is no verified body of evidence that supports the use of IgG testing to diagnose adverse reactions to food, despite some patients reporting improvements in their symptoms (2,3,5). IgG testing is not recognised as an appropriate diagnostic tool for food intolerance, and this is widely agreed upon by governing health bodies worldwide (2,6,7).

If people see improvements, then what’s the issue? 

Although some consumers may report improvement in symptoms upon removing said foods, likely in part due to the placebo effect, the use of these tests is not without their dangers. Many of the foods listed are hard to avoid in any normal diet and often leads to unnecessary dietary restriction with little or no guidance from a qualified healthcare professional. Consumers often make long-term, strict changes to their diet resulting in a decreased quality of life and possible risk of malnutrition and associated health issues (2). What's more, seeing as these tests are unable to properly identify an allergen, a patient may not avoid a food that they actually need to, as a result of a true allergy or intolerance. 

The bottom line 

Food sensitivities should only be established on the advice of an allergist, immunologist, or registered dietitian who are specialists in the field. A combination of diagnostic tools such as food challenges, skin prick testing, and consideration of a complete medical history, is really the only validated method for identifying food sensitivity or intolerance.

References

1. Lavine, E. (2012). Blood testing for sensitivity, allergy or intolerance to food. CMAJ, 184(6), 666–668.

2. Carr, S., Chan, E., Lavine, E., & Moote, W. (2012). CSACI Position statement on the testing of food-specific IgG. Allergy, Asthma, and Clinical Immunology : Official Journal of the Canadian Society of Allergy and Clinical Immunology, 8(1), 12.

3. Kelso, J. M. (2018). Unproven Diagnostic Tests for Adverse Reactions to Foods. The Journal of Allergy and Clinical Immunology: In Practice, 6(2), 362–365.

4. Stapel, S. O., Asero, R., Ballmer‐Weber, B. K., Knol, E. F., Strobel, S., Vieths, S., & Kleine‐Tebbe, J. (2008). Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report*. Allergy, 63(7), 793–796.

5. Antico, A., Pagani, M., Vescovi, P. P., Bonadonna, P., & Senna, G. (2011). Food-specific IgG4 lack diagnostic value in adult patients with chronic urticaria and other suspected allergy skin symptoms. International Archives of Allergy and Immunology, 155(1), 52–56.

6. Australian Society of Clinical Immunology and Allergy. (2017). Unorthodox Testing and Treatment for Allergic Disorders. https://www.allergy.org.au/hp/papers/unorthodox-testing-and-treatment

7. Block, S. A. (2010).AAAAI support of the EAACI Position Paper on IgG4. Journal of Allergy and Clinical Immunology, 125(6).