Food Intolerance Test in Australia

What a food intolerance test is — and what it is not

Food intolerance is a non-immune reaction to a food component, distinct from food allergy, and unlike allergy it has no single validated blood test.

Food allergy is an IgE-mediated immune reaction. It is rapid, reproducible and measurable, and skin prick testing or specific IgE blood testing has an established role when interpreted by a doctor alongside clinical history. Food intolerance is a different mechanism entirely: an enzyme deficiency such as lactase deficiency, a pharmacological response to food chemicals, or an osmotic and fermentative effect from poorly absorbed carbohydrates such as FODMAPs.

The commercially marketed 'food intolerance test' is usually a panel measuring IgG or IgG4 antibodies against dozens or hundreds of foods, sold direct to consumers online. The Australasian Society of Clinical Immunology and Allergy (ASCIA) — the peak body for allergy and clinical immunology in Australia and New Zealand — advises that IgG food antibody testing is not a validated method for diagnosing food intolerance or allergy and should not be used for that purpose.

The reason is mechanistic, not merely statistical. IgG antibodies to food proteins are a normal consequence of eating those foods; their presence reflects exposure and immune tolerance, not intolerance. Consequently a panel will flag the foods you eat most, which is why results so often list staples such as wheat, dairy and eggs. Acting on them risks unnecessary dietary restriction, nutritional deficiency, disordered eating patterns, and delayed diagnosis of a real underlying condition.

Why people seek food intolerance testing

People seek testing because of genuine, persistent symptoms — bloating, abdominal pain, altered bowel habit, fatigue, headache or skin changes — that appear to follow eating.

Those symptoms are real and common. Irritable bowel syndrome alone affects a substantial proportion of Australian adults, and food is a recognised trigger for many people who have it. The problem is not the question being asked; it is that the test being sold does not answer it.

The clinically useful sequence starts by excluding conditions that are diagnosable with validated tests, because several of them present exactly as 'food intolerance'. Coeliac disease is the clearest example: it affects roughly one in 70 Australians and remains substantially underdiagnosed, and it has accurate serology. Lactose malabsorption has a validated hydrogen breath test. Inflammatory bowel disease, thyroid disease, iron deficiency and, in older adults, colorectal pathology all need consideration before symptoms are attributed to intolerance.

Only once those are excluded does a structured elimination and rechallenge — supervised by a GP and an Accredited Practising Dietitian, often using the low-FODMAP protocol developed at Monash University — become the appropriate way to identify individual triggers. It remains the reference standard, because it tests the actual hypothesis: does removing this food change your symptoms, and do they return when it is reintroduced?

What a positive result can indicate

A positive coeliac serology indicates a high likelihood of coeliac disease and is a reason to see your GP for confirmation, not to start a gluten-free diet.

Raised tissue transglutaminase IgA, particularly at high titre and with a positive deamidated gliadin peptide antibody, makes coeliac disease likely. Australian practice is to confirm with a small bowel biopsy performed while still eating gluten, because starting a gluten-free diet before biopsy can normalise the intestinal lining and make definitive diagnosis impossible.

Raised inflammatory markers or an abnormal full blood count in someone with gut symptoms point away from simple intolerance and towards inflammatory or structural bowel disease, which needs GP assessment and often gastroenterology referral.

A positive result on an IgG food antibody panel, by contrast, indicates that you have eaten the food. It is not a reason to eliminate it.

What a negative result can indicate

Negative coeliac serology in someone eating adequate gluten makes coeliac disease unlikely, but it does not exclude food-related symptoms from other mechanisms.

A negative result is genuinely useful: it removes the most important diagnosable cause from the list, and it means gluten restriction is unlikely to be the answer. One caveat matters — around one in 40 people with coeliac disease also have selective IgA deficiency, which produces a falsely negative IgA-based result. That is why total IgA is measured alongside the antibody.

The other caveat is dietary. If you have already been avoiding gluten, serology can be negative regardless of whether you have coeliac disease. Adequate gluten intake for at least six weeks before testing is required for the result to mean anything.

With coeliac disease and other organic causes excluded, the next step is not a broader antibody panel. It is a supervised elimination-and-rechallenge process with a dietitian, which identifies triggers with far better accuracy and far less unnecessary restriction.

Which tests are evidence-based in Australia

Australian clinical bodies support coeliac serology, specific IgE testing for suspected allergy and hydrogen breath testing for carbohydrate malabsorption — and advise against IgG food antibody panels.

Who should consider testing

Blood testing is worthwhile for anyone with persistent gut symptoms, unexplained fatigue or iron deficiency in whom coeliac disease and other organic causes have not yet been excluded.

See your GP promptly rather than testing first if you have blood in your stool, unintentional weight loss, difficulty swallowing, persistent vomiting, or symptoms that began after age 50.

• Persistent bloating, abdominal pain, diarrhoea or constipation that follows eating.
• Unexplained iron deficiency, low B12 or low vitamin D suggesting malabsorption.
• A first-degree relative with coeliac disease, type 1 diabetes or autoimmune thyroid disease.
• Unexplained fatigue, mouth ulcers, or unexplained weight loss.
• Before starting a gluten-free diet — testing afterwards is unreliable.

How testing works with FORM in Australia

FORM issues an accredited-lab pathology request for the evidence-based panel, and returns a written interpretation for you to take to your GP or dietitian.

FORM does not sell IgG food antibody panels, hair analysis or other unvalidated intolerance tests, and does not provide dietary treatment. We provide accredited pathology and a clear explanation of what it shows.

• Order online — no GP referral required.
• Keep eating gluten until after your blood is collected if coeliac disease is being assessed.
• Attend a NATA-accredited (ISO 15189) collection centre.
• Receive a written, plain-English report.
• Take the report to your GP or an Accredited Practising Dietitian to plan next steps.