Food Allergy and Intolerance Testing

The number of people seeking help for food intolerances and allergies is on the rise. Unfortunately, not all of the tests available are accurate or reliable. Many common and easy to access allergy tests are expensive and don’t actually test for what they say they do. Food allergies and intolerances vary in severity but all need to be managed effectively to look after your digestive system to prevent damage and nutritional deficiencies. 

If you suspect you have an allergy or an intolerance it’s important to make sure you have the right testing for an accurate diagnoses. 

Symptoms of food allergy, intolerance and sensitivity

Gastrointestinal issues  can be caused by a wide number of things and symptoms often vary between individuals. Causes include

• Allergy
• Intolerance
• Irritable Bowel Syndrome (IBS)
• Sensitives (alcohol, caffeine and chilli are common irritants that are often overlooked).

It’s easy to suspect common allergens as the culprit for symptoms, but they aren’t always obvious.

Food Allergy vs Food Intolerance

A food allergy is an abnormal immune-mediated response to an otherwise harmless food. Food allergies are categorised as IgE mediated, non-IgE mediated and mixed. IgE mediated food allergies usually cause immediate and sometimes life threatening symptoms like anaphylaxis. We often see these symptoms with peanuts and shellfish. Non-IgE mediated allergies are less well understood but have a more delayed response (usually occurring within a few hours of consumption)  and typically cause symptoms like vomiting and diarrhoea (commonly seen with cows milk protein or soy protein).

A food intolerance is a response to a food that DOES NOT involve the immune system. Usually food intolerances cause symptoms like nausea, vomiting, flatulence, constipation/diarrhoea or rashes. Symptoms appear as the body cannot digest a food or chemical very well.  Common food intolerances include MSG, salicylates, amines, lactose and wheat.

Should Everyone Avoid Dairy, Gluten and Wheat?

Many sources recommend everyone avoid common allergens like dairy, gluten or wheat. This is poor information…. These foods do not cause damage or inflammation in people who can tolerate them. An allergy or intolerance is an abnormal reaction. Excluding food groups from your diet puts you at risk of nutritional deficiencies. For people with allergies, this is a justified risk. For everyone else, it’s unnecessary and potentially harmful. It’s as silly as saying that everyone should avoid eating nuts because some people have a nut allergy. 

Testing for Food Allergies and Intolerance 

There are many testing options available and they becoming increasingly popular as people want to get to the bottom of their upset stomachs. Unfortunately, not all of them are accurate or give you the answer you actually want or need. This process needs to be done under medical supervision and isn’t the sort of thing you can do yourself with a kit bought over the internet. If you suspect you have a food allergy, you need to see your GP to have this diagnosed. Your GP may be able to do this or they may refer you on.

Formal diagnosis (through a medical doctor ) is essential for an accurate diagnosis. It will also help you to determine specific prevention and treatment strategies and to rule out any other potentially series conditions or complications. You will also get the most up-to-date and relevant information for safely managing your condition. Methods of diagnosis through a medical doctor are eligible for Medicare rebates. 

Skin Prick Testing for Food Allergies

Medical Doctors can do a skin prick test to diagnose allergies. This is the gold-standard of allergy testing. A tiny amount of the suspected allergen is placed on the skin which is then pricked to allow it to enter the skin. A response at the site of the prick will indicate if an allergy is present or not and also how severe it is. 

IgE Testing for Food Allergies

Another reliable test that can be done is IgE blood testing (this used to be called RAST testing). It is used to detect specific allergies that illicit an immune response, but isn’t as useful as the skin prick test. This testing measures antibodies against specific allergens with an individual test being required for each suspected allergen. 

Total IgE Antibodies tests aren’t very useful as they measure the total antibodies in a blood sample, as opposed to the response from a single allergen. People with allergies can have normal total IgE levels and people without allergies can have elevated levels from parasitic infections and other health conditions.

Many people already know if they have IgE mediated allergies as they cause immediate symptoms and can be life threatening.  These are the ones we need to be seriously concerned for. They can cause itching skin, throat swelling, vomiting and even anaphylaxis. 

A food intolerance will not show up on an IgE mediated test.

Testing for Coeliac Disease (Gluten Allergy)

Coeliac Disease is an allergy to gluten. A symptom diary, family history check and blood tests (after a period of eating gluten) can suggest Coeliac Disease. It can only be diagnosed with a biopsy of the small bowel which is used to check for damage. 

IgG Testing for Food Intolerance

The tests you see advertised online and recommended by alternative health practitioners are IgG tests. IgG is an antibody that responds to certain foods (not an allergy or intolerance). It is an immune marker showing us that your body recognises and has been exposed to this food before. This is not a sign of a negative reaction, in fact, it’s often a sign of a good level of tolerance to that food.

An increased IgG test in children who have a cow’s milk allergy, shows that they are outgrowing the allergy and are better able to tolerate it. Remember that a food intolerance by definition does not actually involve the immune system.

I see many clients who have had these expensive tests done and they almost always come back high for dairy and wheat. That’s because us Australian’s typically eat a lot of diary and wheat. An IgG response to these foods is just telling us that your body recognises them! The foods you eat most of will show higher levels of exposure. The more wheat you eat, the higher your response will be. This isn’t a bad thing. In fact, the IgG response is likely to actually indicate that you CAN tolerate that particular food.

International immunology and allergy experts agree that there is no credible evidence to support the use of IgG testing for food allergies or intolerances 1, 2, 3. The bottom line, IgG tests do not show food intolerance or sensitivities.

See a Dietitian to test for Food Intolerances and Sensitivities

For a suspected food intolerance, you will need to see a medical doctor or dietitian. An intolerance will not show up on an allergy test. A dietitian is the only nutrition professional that can diagnose conditions, a naturopath cannot diagnose conditions (but many will happily sell the unreliable IgG tests). The gold standard for diagnosis of an intolerance is through a process of elimination and re-introduction. Because food intolerances have varying degrees of sensitivity, the elimination/reintroduction process lets us understand just how much of that food is required for an intolerance symptom to develop. This process should be done under the guidance of a medical doctor or qualified dietitian (or a university-educated nutrition professional who specialises in food intolerance – if said person offers IgG testing, walk/run away).

Holistic or alternative health-care practitioners are not qualified to do this and will more than likely advocate for unreliable method that they can provide (and charge you for) like hair analysis, VEGA, Bicom or IgG testing. If someone suggests you do any of these unproven tests, they are not experienced and knowledgeable enough about intolerances and allergies.

I think I have a Food Allergy or Intolerance

If you suspect that you do have a food allergy or intolerance it is important to get this investigated by an appropriately qualified individual. Even credible medical tests only tell part of the story and it isn’t always easy to tell which food or is causing your symptoms. You may be missing an important diagnosis or avoiding the wrong foods if trying to self-manage your symptoms.

Keep a food and symptom diary for a few days and keep an open mind about the potential culprits. Look for any obvious food triggers and take this to your GP for analysis or a referral.

Many people turn to alternative practitioners when they haven’t had success managing their symptoms with their regular medical doctor. Remember that these practitioners are not qualified to diagnose or manage these conditions. Always be your own health advocate and don’t be afraid to get a second opinion from another medical doctor or a referral to an expert, like an immunologist or an Accredited Practicing Dietitian. 

1. Australasian Society of Clinical Immunology and Allergy

2. American Academy of Allergy, Asthma and Immunology

3. European Academy of Allergy and Clinical Immunology

Sarah Moore is a mum, and university qualified Registered Nutritionist with a decade of experience working with families to improve their health and well-being. Sarah has a simplistic and practical approach to family nutrition and can help the overwhelm of eating and living well with private consultations, email Q&A and her school lunchbox ebook. You can also find her on Facebook and Instagram for more healthy tips and tricks.