Food Intolerance And Allergy Tests – The Complete Guide (2021)

Do you wonder if a certain food is causing you problems? Perhaps you can’t pinpoint why you get migraines, or you suspect that food is behind your sinus or skin issues.

The problem with food sensitivities is they cause a broad range of symptoms—from obvious digestive signs such as bloating, diarrhoea and abdominal pain, to less obvious ones like migraines and brain fog.

The other difficult thing about food sensitivities is that symptoms can take anywhere from a few hours to three days to manifest, which makes it tricky to identify the true cause. What’s more, it can be hard to tell if it’s actually the food causing the issue, or another digestive condition, such as leaky gut, IBS or SIBO.1

This article will talk you through food sensitivities, the tests available and what to do if you think certain foods are causing you problems.

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What is food intolerance?
How to test for food intolerance
What is a food intolerance test?
Where can I get a food intolerance test in the UK?
Which food intolerance test is best?
How to test for food intolerance in children
How to test for food intolerance with the NHS
How do doctors test for food intolerance?
How much does food intolerance test cost?
How to read food intolerance test results
What is the best test for food intolerance?
What is IgG food intolerance test?

What is food intolerance?

There are three types of food reactions and—although their symptoms can be similar—they have important physiological differences. Let’s take a look at each:

Food sensitivity is when the body produces immunoglobulin G (IgG) antibodies as part of an immune reaction. This typically happens when too-large bits of food get into the bloodstream due to leaky gut.

IgG immune reactions can be slow to appear. This means that a person could eat food to which they are sensitive but not experience any symptoms until a few days later. If the problematic food enters the bloodstream on a continuous basis, the immune system undergoes constant activation—leading to chronic inflammation.

Food intolerance is a term for food reactions that arise from compromised digestion. This kind of reaction does not affect the immune system. Food sensitivities and intolerances are not life-threatening, but they can be easily confused without the correct diagnosis.

Food allergy is when the body launches an immediate IgE immune response. This needs immediate medical attention. To learn more about the differences, visit Are food allergy and food intolerance the same?

People react to food differently due to two driving factors:

Genetics. Food reactions, especially severe IgE allergies, can be passed down in families.2

Environment. There are many factors that can influence our immune system, including exposure to infection, gut bacteria, lifestyle, exposure to toxins, whether we have pets, vitamin D status and whether we were breastfed or not3,4.

It can be difficult to get a diagnosis for food reactions. This is because some of the symptoms of food allergies, sensitivities, intolerances as well as other gut-related conditions overlap. It’s important to understand what trigger foods are causing your problems before you start restricting your diet.

How to test for food intolerance

To understand what foods could be problematic for you, you can either try an elimination diet or take food intolerance test, and then monitor your symptoms.

1. Try an elimination diet. This involves removing reactive food(s) from your diet and monitoring your symptoms for up to eight weeks. Foods are then reintroduced one-by-one to see if your symptoms return. For guidance on conducting an elimination diet, you may wish to speak to a Registered Nutritional Therapist

2. Take a food sensitivity test. Confusingly, these are often referred to as ‘food intolerance tests’, even though they actually test for food sensitivities. For ease, we’ll use these terms interchangeably in this article. This sort of test looks at your blood chemistry to see which IgG proteins are present, providing insight into how your body is responding to certain foods. A food intolerance test takes some of the guesswork out of an elimination diet, but your results still need to be considered in light of your overall health.

But, remember: food reactions have similar symptoms to other gut-associated conditions, which makes it tricky to pinpoint the exact cause.

Many times, if you’re reacting to several foods, it’s not actually a specific food sensitivity that’s at the root of your problems. It’s that the health of your gut is compromised and needs a little attention. Usually, once you address and restore gut function, you can go back to enjoying the perceived problematic foods.

What is a food intolerance test?

A food sensitivity or food intolerance test aims to identify foods that may be causing problems for you. They can’t definitively show that one food causes a specific symptom, but they can guide you in personalising your diet.

Antibody food sensitivity tests will usually measure the production of immunoglobulin G (IgG) antibodies to between 50–100 reactive foods. These can include dairy, grains, fruits, nuts and seeds. Again, an IgG test does not confirm a diagnosis of food sensitivity but—when looked at in combination with your overall health—it provides some useful clinical data.5

It’s also important to address what’s causing the symptoms in the first place. It could be inflammation of the gut wall lining, which will need adequate gut support. Other causes include stress, excess alcohol, antibiotics and bacterial and viral infections, SIBO, yeast and parasites, to name a few!

The Healthpath Food IgG Finger Prick Test measures foods that are commonly associated with food sensitivity. Your report comes with a bespoke supplement plan based on your test results and symptoms, plus a personalised food list for supporting gut repair. You also receive a complimentary Healthpath Foundations of Health education programme to support your health journey.

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Where can I get a food intolerance test in the UK?

There are many online home test kits and food intolerance labs, and it’s hard to work out which are reliable.

Individual labs vary in their testing methodologies, and some have poor reproducibility, which means if the same test were conducted twice, different results could be found.

The best food intolerance tests measure your IgG antibodies against specific foods, while also considering your symptoms.

The Healthpath Food IgG Finger Prick Test measures 64 commonly reactive foods. Your results will indicate if a food is problematic, borderline or considered safe/non-reactive. While some tests measure more foods, we find that testing the most common allergenic foods provides the most clinically meaningful data when considered in combination with your symptoms.

Which food intolerance test is best?

There are various ways to test for food intolerances, including online home tests, lab-offered food intolerance tests, elimination diets, and alternative testing methods.

Let’s take a look at each:

Skin prick tests
These test kits can be used at home, as they provide a sterile needle to prick your skin and obtain a blood sample. You can then post your blood sample back to the lab for testing. There the blood is exposed to a panel of food components, and the amount of IgG binding to each food can highlight suspected food sensitivities.

Blood tests
These can’t be carried out at home because they require blood to be drawn by a phlebotomist. They measure serum to detect IgE and IgG levels in the blood. Some labs will also offer full antigen blood testing profiles, which include markers of inflammation such as cytokines, CD3 and IgG4 markers.

Oral food challenges and elimination diets
This is where you’re given a small amount of a suspected food to eat, and then wait to monitor any symptoms. This requires dedication and should be carried out with practitioner support to ensure you’re eliminating and reintroducing the right foods at the right time.

Other tests
These include kinesiology or muscle testing, hair analysis and vega testing (which measures electromagnetic conductivity in the body). These tests are promoted online as a means to diagnose food intolerances, but there’s no evidence to support their validity.6,7

How to test for food intolerance in children

According to NICE, food allergies are on the rise. But in 20% of cases, people avoid certain foods without getting a confirmed diagnosis because they’ve heard they can be problematic.8

Children and babies are most at risk of food allergies and food sensitivities because their immune and digestive systems are still developing. It’s likely this is due to a combination of both genetic and environmental factors. Increased caesarean birth rates, lack of early-age exposure to germs and declining breastfeeding rates may also play a role.9

As their immune system is still developing, food antibody IgG testing in infants under two years of age is not recommended.10 If you think your child is at risk of intolerances, it’s best to speak to your GP or a specialist, as removing certain food groups from your child’s diet may influence their growth and development.

Thankfully, some babies and children will outgrow food sensitivities as their immune systems become more robust. But some foods will remain problematic. Severe allergic reactions are rare but, if a child (or adult) has experienced anaphylaxis, they will need to avoid the offending foods for life. This type of food allergy affects the entire body and requires immediate attention.

How to test for food intolerance with the NHS

Food intolerance tests aren’t offered by the NHS, but a Registered Nutritional Therapist or other specialist will be able to run these tests for you. They might ask you to keep a food diary to pinpoint the culprit food. A detailed case history with the right testing will get to the bottom of what’s causing the issue.

How do doctors test for food intolerance?

A GP will ask questions if they think you have any issues with food allergies and intolerances. This will usually include an investigation around the symptoms you are experiencing, the onset and severity. A GP will refer you to a specialist if they think you have food allergies or intolerances, but only after they have ruled out any underlying medical conditions.

How much does food intolerance test cost?

Online test kits, laboratory food intolerance tests and alternative methods for testing can range from anywhere from £50 to £450, depending on which foods and biomarkers are included.

While there are many options available, it’s best to look for a food intolerance test that considers both your tests results and personal health history to understand what is truly behind your symptoms.

How to read food intolerance test results

Food intolerance test results are usually reported based on category i.e. dairy, fruits and vegetables, seafood/fish and grains etc. A positive food intolerance result means that IgG antibodies have been detected against the tested food. This is indicated on a test report as a food in the ‘red’.

Some important considerations when reading food intolerance tests include:

· Regular exposure to an unvaried diet can increase IgG levels.11

· Leaky gut or other gut imbalances can increase our sensitivity to food, and therefore cause IgG levels to go up.

· The presence of IgG antibodies to a specific food can increase in response to an allergic (IgE) reaction going down.12

· Some people will also have high IgG levels on their test results and not have any symptoms.

As we have said, if your test results show you have food sensitivities, it’s important that you look at your test results in the context of your overall health and symptoms. There could be a different reason why your body is producing IgG antibodies. Elevated levels of IgG antibodies have been linked to IBS, obesity, depression and chronic inflammatory conditions.13,14

The Healthpath Food IgG Finger Prick Test provides you with a detailed report, which is reviewed by one of our qualified practitioners alongside your symptom survey. We believe that supporting gut repair, while reducing exposure to IgG-positive foods, may reduce the overall antigen load and reduce IgG levels—and therefore improve symptoms.

The good news is that some food sensitivities can improve over time. This usually requires temporary avoidance of any food triggers and a focus on improving gut health.

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What is the best test for food intolerance?

The most reliable food intolerance tests are those that measure food-specific IgG reactions in blood. This can be done using a simple pin-prick blood sample.

Healthpath offers a simple at-home finger prick blood test kit to assess 64 of the most commonly reactive foods. Based on your results, you’ll receive a personalised action plan that covers diet, supplements, gut repair and lifestyle habits.

What is IgG food intolerance test?

A food-specific IgG test measures the presence of IgG antibodies against food. By measuring IgG in the blood, it’s possible to work out which foods you may be sensitive to. This kind of test provides some useful information about your gut health too.15

There is controversy over measuring IgG and the validity of its use in clinical practice, but high levels of IgG antibodies against food is not considered a normal physiological response. We believe that food-specific IgG testing—when combined with a detailed symptom analysis—can provide useful information.

Studies back this up. One clinical trial found that people who personalised their diets based on food-specific IgG testing experienced an improvement in migraine symptoms.16

If you test positive for a food-specific IgG test, it doesn’t necessarily mean that that specific food is causing your symptoms. But the benefit of doing a food intolerance test is that it quickly shows you which foods may be a potential problem, which can help you create a targeted elimination diet. Testing can also look at some of the uncommon foods which you may not have considered.


Mechanisms of the immune system are complex. Because symptoms of food sensitivities can be different from one person to the next, it’s hard to associate a specific food to one single cause. We all respond to reactive foods differently.

Getting to the bottom of a food intolerance or food sensitivity isn’t as simple as avoiding foods that have come up on your test results as ‘problematic’. It’s important that you address the root cause too, which typically involves working on your gut health. It’s also important that you receive nutritional guidance so you don’t miss out on key nutrients from the foods you’ll be missing.

If underlying issues aren’t resolved, you may become reactive to more foods and chronic inflammation can persist. A food intolerance test can be a useful tool to start you on your journey of self-investigation, helping you to adjust your diet and lifestyle for optimum health.

Tegan Philp BA PgDip MSc is a Registered Nutritional Therapist. Passionate about all things gut-related, her master’s dissertation was on the role of the microbiome in cardiovascular outcomes. Tegan has over eight years’ experience working for leading nutrition colleges in both Australia and the UK. You can learn more about Tegan on her practitioner page or connect with her via LinkedIn.



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