Food Intolerances: to test or not?

understanding if it is a food intolerance

If you’re experiencing digestive symptoms, it’s normal to think it’s because of a food intolerance. So, it makes sense why many people end up buying the widely available food intolerance tests. But are these tests actually legit or are they just emptying your wallet?

In this article I’ll discuss some of the different types of tests available, whether they’re credible and trustworthy or not, and how food intolerances should be diagnosed.

IgG Food Intolerance Tests

You may have heard of the York Test, and there’s other IgG “panel” tests widely available to buy directly, or through a nutritionist or nutritional therapist. 

I can tell you now that a Registered Dietitian will NEVER recommend one of these tests.

> The proposed theory

IgG panels are designed to look for IgG4 in the blood, which is an antibody produced by our immune system with the job of protecting us against pathogens (things that harm our body). 

A positive result to a particular food (they usually test for up to 100 different foods) is suggesting that you have a food intolerance because your immune system has produced antibodies. The recommendations are then to remove that food, or often multiple foods, from the diet. 

> The truth according to the science

The thing is, the release of IgG4 is a NORMAL response of our immune system to exposure of foods. It’s just our body checking that there’s not a pathogen coming in that needs a response. 

Often you’ll see positive IgG4 results without any corresponding symptoms – one the reasons why the list of “intolerances” someone gets “diagnosed” with can be much bigger than just one or two foods. 

These tests have never been scientifically proven to achieve what they are trying to achieve. Any scientific studies that were the basis for these IgG tests are outdated, and in non-reputable publications. The lack of evidence to support their use has meant that many worldwide organisations involved in allergy and immunology have specifically recommended against the use of IgG tests as a method of diagnosis of food intolerances. 


You may have heard of kinesiology as a non-invasive technique for testing for food intolerances.

Once again, a Registered Dietitian will NEVER recommend one of these tests.

> The proposed theory

These tests look at muscle responses to vials of extracts of different foods placed on the stomach. If the muscles don’t respond ‘properly’ then it indicates a food intolerance, which can be if there’s a corresponding symptom or not. 

> The truth according to the science

There is no scientific basis for this type of test. 

Hair Analysis

Perhaps one of the less common tests, but still out there and used by some alternative practitioners. 

Yes you’ve guessed it, a Registered Dietitian will NEVER recommend one of these tests.

> The proposed theory

A sample of hair is sent for testing through a laboratory to identify a food intolerance by scanning the energy fields in the hair and comparing results to a database.

> The truth according to the science

Whilst hair analysis can be used to test for recreational drug use and heavy metal poisoning, there’s no science to support the use of this to identify food intolerances. 

Why does cutting foods out improve symptoms if it’s not an intolerance?

Often people report a huge improvement in their symptoms following removal of multiple foods. This could be due to different reasons:

  • The placebo effect: the gut-brain connection is real, and it’s strong. If we believe that something triggers symptoms we know we’re more likely to experience symptoms. Similarly, by cutting things out we might be psychologically tricking ourselves into a reduction in symptoms.
  • By removing lots of foods from the diet, it’s likely that we’re reducing the amount of foods containing highly fermentable carbohydrates (aka FODMAPs). We know that for those with Irritable Bowel Syndrome (IBS), FODMAPs can trigger symptoms as the gut lining is hypersensitive which means the individual feels the increase in fluid or gas in the large intestine as our gut microbes ferment on the foods. 

If it’s not food intolerances, then what is it?

In the case of IBS, where often food triggers are identified, we’re not dealing with a true food intolerance as the reaction is due to the aforementioned hypersensitivity in the gut. Often by treating IBS through diet and non-diet approaches these sensitivities can be reduced and often improve over time. 

How are food intolerances really diagnosed?

There are true food intolerances that exist, for example:

  • Lactose
  • Gluten
  • Fructose
  • Histamine
  • Sulphites
  • Salicylate

Whilst diagnosis can be tricky and time consuming, especially if someone has multiple intolerances, it is important to follow the correct steps. 

The gold standard method is:

  1. Exclude the food(s)
  2. Record whether symptoms are resolved
  3. Reintroduce the food to see if the symptoms return. This is the most important part of the process which people often miss!

So you can see that no testing is required for this. 

Food is complex, and sometimes there could be multiple elements that a person could be intolerant to which is why this process should always be guided by a Registered Dietitian who has experience in food intolerances and sensitivities. 


Please don’t self-diagnose food intolerances through pricey home testing kits or via alternative practitioners. There just isn’t the evidence to support the use of those tests and so you’re essentially throwing your hard earned money away I’m afraid!

The only validated method for diagnosing a food intolerance is the exclude and reintroduce method, which should always be guided by a Registered Dietitian who will also make sure your diet remains nutritionally adequate throughout the process. I can help with this!

* Note that this article covers food intolerances only. Food allergy, which involves an immune response and can be life threatening, is quite different. There are validated tests for allergies that should be carried out under medical supervision.


Stapel SO, Asero R, Ballmer-Weber BK, et al. Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report. Allergy. 2008;63(7):793-796. doi:10.1111/j.1398-9995.2008.01705.x

Wong KH, Horwitz R, Soffer GK. Immunoglobulin G food testing. Ann Allergy Asthma Immunol. 2021;126(6):611-612. doi:10.1016/j.anai.2021.01.022

Hammond C, Lieberman JA. Unproven Diagnostic Tests for Food Allergy. Immunol Allergy Clin North Am. 2018;38(1):153-163. doi:10.1016/j.iac.2017.09.011

Teuber SS, Porch-Curren C. Unproved diagnostic and therapeutic approaches to food allergy and intolerance. Curr Opin Allergy Clin Immunol. 2003;3(3):217-221. doi:10.1097/00130832-200306000-00011

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