Having started out in private practice I am amazed at the amount of practitioners selling food allergy and food intolerance testing often for large sums of money. The truth is most of these tests are a complete waste of money and can lead to nutritional deficiencies and a lot of stress, expense and time wastage when trying to avoid the foods suggested.

Again here it is a case of buyer beware – it is important that you check out the credentials of the person doing the test and what exact test they are completing. In Ireland the only recommended health professionals to do allergy testing is your GP or allergy doctor or immunologist. When it comes to food intolerance testing there is in fact no scientific test that you can do to diagnose food intolerance. The only way to diagnose a food intolerance is to do an exclusion diet and it is recommended you consult with a CORU Registered Dietitian to complete this process.

What is the difference between food allergy and food intolerance?

A 'food allergy' is a reaction that involves the immune system, which is the body’s defence against foreign bodies. Those that do not involve the immune system are called a ‘food intolerance’. 

Common food allergy terms:

Medical terms for food allergy and intolerance can be confusing. Here are some common terms and what they mean.

IgE mediated food allergy

This reaction involves IgE antibodies, which your immune system produces. The signs and symptoms of the reaction are rapid and can be severe. Conventional allergy testing, and a detailed allergy-focused clinical history, can help with diagnosis.

Non-IgE mediated food allergy

This reaction involves the immune system, but not IgE antibodies. Signs and symptoms of a reaction are delayed or ‘slow onset’. Allergy testing is not helpful. A detailed allergy-focused clinical history, can help with diagnosis. Exclusion and reintroduction of the suspected 'culprit' food(s) lead to diagnosis.

Non-allergic food hypersensitivity

The immune system is not involved in this type of reaction. It is also known as food intolerance. Exclusion and reintroduction of the suspected 'culprit' food(s) lead to diagnosis.

Conventional Allergy Testing:

These tests are evidence-based and performed by registered health professionals, typically your GP or an allergy doctor or immunologist.

Skin prick test

A small amount of diluted allergen (the protein we suspect you are allergic to) is placed on your skin and then your skin is pricked. If a small swollen lump or ‘weal’ appears, in conjunction with a detailed clinical history, an IgE mediated food allergy may be diagnosed. This test is only performed under medical supervision.

Blood tests

A specific IgE test measures the amount of IgE antibodies to a suspect food in the blood. This is called a Radio Allergo Sorbent Test (RAST). Your results will give a diagnosis of IgE mediated food allergy (along with a detailed clinical history). Your GP or hospital clinician can organise this blood test.

Commercial companies may offer a similar blood test called MAST (Multi-Allergen Screening Test). However, it is difficult to give an accurate diagnosis without your full clinical history.

Food challenges

Starting with a small amount, you will be given the suspect food orally (in the mouth). Your clinician will gradually increase the amount, checking to see if you have any symptoms. You may be aware of the food you are eating, or 'blinded' and unaware of which food you are eating. This test should only be performed under medical supervision with medical facilities and resuscitation equipment available.

Food exclusion and reintroduction

You stop eating the suspected food(s) for a period of time and watch and record your symptoms. If your symptoms improve, then the suspect food is reintroduced. If your symptoms return, this would indicate a problem with that particular food.

This test can be very time consuming. It is best carried out under the supervision of a registered dietitian, especially if involving children. A well-balanced nutritional intake during the test period is important - especially if you are excluding major food groups like dairy or wheat.

Alternative tests:

There are also many commercially available tests that claim to diagnose food hypersensitivity and intolerance

You should avoid these because they have no scientific basis. They can be harmful when multiple foods are excluded without reason, or if they are not reintroduced under guidance of a CORU registered dietitian.

IgG blood test

There are many tests for IgG food intolerances out there. This blood test looks at IgG antibodies to specific foods present in your blood. The test claims that an increase in IgG to a certain food indicates intolerance to that food. IgG antibodies to food are found in all healthy adults & children who do not show any symptoms.

It is important to understand that this test has never been scientifically proven to be able to accomplish what it reports to do. The scientific studies that are provided to support the use of this test are often out of date, in non-reputable journals and many have not even used the IgG test in question. The presence of IgG is likely a normal response of the immune system to exposure to food. In fact, higher levels of IgG4 to foods may simply be associated with tolerance to those foods.

There is currently no convincing evidence to support this test and it is not recommended as a diagnostic tool.

Kinesiology

This is based on the idea that certain foods cause an energy imbalance in the body which is detected by testing the response of the muscle. The therapist would test your muscle response when holding the suspect food in a glass vial.

Studies show that this test is no better than chance and is not recommended.

Hair analysis

A small lock of your hair is sent to a laboratory, where they scan the energy fields in the hair. The results are then compared to a database.

This testing is used for recreational drug use and lead and mercury poisoning. However, its use in allergy testing is unproven and has no scientific basis.

Electrodermal (Vega) test

This test measures the electromagnetic conductivity in your body. It is claimed that an offending food will show a dip in the electromagnetic conductivity.

Research studies show that this test is no better than chance.

The problem with non-evidenced tests

These alternative allergy tests are not based in scientific evidence. They are a waste of your money and may suggest long lists of foods to be excluded from the diet unnecessarily.

Excluding a major food group e.g. wheat or milk, or a combination of different foods, can cause many difficulties. Without proper nutritional advice, a restricted diet can lead to nutritional deficiencies, malnutrition and reduced quality of life.

Summary

• If you think you may have a food allergy, seek proper medical advice. They will discuss the use of evidence-based, conventional allergy testing.
• Alternative allergy testing should be avoided as it has no scientific basis.
• CORU registered dietitians can give you the correct nutritional advice and ensure a well-balanced nutritional intake that will be tasty, varied and culturally acceptable.
• Children should not follow a restricted diet unless supervised by a paediatric dietitian as they need a well-balanced diet to ensure adequate growth and development.