Food Allergy and Intolerance Testing in Australia
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The distinction between a food allergy and a food intolerance is not just academic. It determines which tests are appropriate, how serious the reaction may be, and what kind of specialist care is needed. Using the terms interchangeably, as often happens in everyday conversation, can lead to the wrong type of investigation and unnecessary dietary restriction.
Food Allergy
A food allergy is an immune-mediated response. When someone with a food allergy eats a trigger food, their immune system identifies specific proteins in that food as harmful and mounts a defensive response. In most cases, this involves the production of immunoglobulin E (IgE) antibodies, which trigger the release of histamine and other chemicals from mast cells. This is what causes the visible symptoms: hives, swelling, vomiting, difficulty breathing, or in severe cases, anaphylaxis.
IgE-mediated food allergies tend to produce symptoms rapidly, often within minutes and almost always within two hours of exposure. The reactions can range from mild (localised skin irritation) to life-threatening (anaphylaxis involving the cardiovascular and respiratory systems). ASCIA notes that anaphylaxis is a medical emergency requiring immediate treatment with adrenaline (epinephrine) via an autoinjector such as an EpiPen.
There are also non-IgE-mediated food allergies, which involve a different part of the immune system and tend to produce delayed reactions, primarily affecting the gastrointestinal tract. These are more common in infants and young children and include conditions such as food protein-induced enterocolitis syndrome (FPIES). Non-IgE-mediated allergies are diagnosed primarily through clinical history and supervised elimination diets rather than blood or skin tests.
Food Intolerance
A food intolerance does not involve the immune system in the same way. Instead, it typically reflects the body's difficulty digesting or processing certain food components. The most well-known example is lactose intolerance, where the body produces insufficient lactase enzyme to break down lactose, the sugar found in dairy products. This leads to symptoms such as bloating, gas, abdominal pain, and diarrhoea.
Other common intolerances involve naturally occurring food chemicals such as salicylates, amines, and glutamates, as well as food additives like sulphites and artificial colours. Unlike allergies, food intolerances are generally dose-dependent. A small amount of the trigger food may be tolerated without issue, while a larger amount causes symptoms. This can make intolerances harder to identify, because the relationship between cause and effect is less obvious.
Food intolerances are uncomfortable and can significantly affect quality of life, but they are not life-threatening in the way that severe allergic reactions can be.
Australia has one of the highest rates of food allergy in the world, and the prevalence appears to be increasing, particularly in young children. Research from the HealthNuts study, conducted through the Murdoch Children's Research Institute, found that more than 10 per cent of 12-month-old infants in Melbourne had a confirmed food allergy.
The most common food allergens in Australia, as identified by ASCIA, include:
- Cow's milk — one of the most common allergies in infants and young children, though many children outgrow it by school age
- Egg — another common childhood allergy, with many children developing tolerance over time
- Peanut — one of the most common triggers for anaphylaxis in children and often persists into adulthood
- Tree nuts — including cashew, walnut, almond, hazelnut, and pistachio; tree nut allergies are frequently lifelong
- Wheat — distinct from coeliac disease, which is an autoimmune condition rather than a classic IgE-mediated allergy
- Soy — more common in infants and young children, with many outgrowing the allergy
- Fish and shellfish — shellfish allergy in particular tends to develop in older children and adults and is usually lifelong
- Sesame — Australia was one of the first countries to recognise sesame as a major allergen and require it on food labels
It is worth noting that any food can theoretically cause an allergic reaction. The list above represents the most commonly reported triggers, but GPs and allergists regularly see patients with allergies to less common foods as well.
Food allergy testing in Australia follows a structured, evidence-based pathway. The starting point is always a thorough clinical history taken by a GP, who will ask about the nature of the symptoms, how quickly they appeared after eating, which foods were consumed, and whether there is a personal or family history of allergic conditions such as eczema, asthma, or hay fever (collectively known as atopy).
Skin Prick Testing
Skin prick testing (SPT) is one of the most widely used methods for investigating IgE-mediated food allergies. It is typically performed by an allergist or immunologist, though some GPs with appropriate training also offer the test.
During a skin prick test, a small drop of allergen extract is placed on the forearm or back, and the skin is gently pricked through the drop with a lancet. If IgE antibodies to that allergen are present, a small raised wheal (similar to a mosquito bite) will appear within 15 to 20 minutes. The size of the wheal helps the clinician assess the likelihood of a true allergy, though it does not predict the severity of a reaction.
ASCIA emphasises that skin prick tests should always be interpreted alongside clinical history. A positive result indicates sensitisation (the presence of IgE antibodies) but does not automatically confirm a clinical allergy. Some people test positive to a food they eat without any symptoms, which is known as asymptomatic sensitisation.
Specific IgE Blood Tests
Specific IgE blood tests (sometimes referred to by older brand names such as RAST tests, though the technology has evolved considerably) measure the level of IgE antibodies to specific food proteins in the blood. These tests are useful when skin prick testing is not practical, for instance if a patient has extensive eczema covering the test area, is taking antihistamines that cannot be safely stopped, or has a history of severe anaphylaxis where even skin testing carries a small risk.
Like skin prick tests, specific IgE blood tests indicate sensitisation rather than confirmed clinical allergy. A GP can order these tests through a standard pathology request, and Medicare rebates apply when the tests are clinically indicated.
Oral Food Challenges
The oral food challenge is considered the gold standard for diagnosing food allergy. It involves the patient eating gradually increasing amounts of the suspected trigger food under medical supervision, usually in a hospital outpatient setting or a specialist allergy clinic. The clinician monitors for any signs of an allergic reaction throughout the process.
Oral food challenges are used in several situations: to confirm a suspected allergy when skin prick and blood test results are inconclusive, to determine whether a child has outgrown an allergy, or to establish the threshold dose that triggers a reaction. Because of the risk of a reaction, these challenges are always conducted in a controlled clinical environment with resuscitation equipment available.
Tests That Are Not Recommended
ASCIA and the RACGP explicitly advise against several types of tests that are marketed to consumers but lack scientific evidence. These include IgG food antibody tests, cytotoxic food testing (Alcat test), Vega testing, kinesiology, hair analysis, and iridology. IgG antibodies to foods are a normal part of the immune response and reflect exposure to a food, not allergy or intolerance. Relying on unvalidated tests can lead to unnecessary dietary restrictions, nutritional deficiencies, and delayed diagnosis of the actual problem.
Testing for food intolerance follows a different pathway than allergy testing, largely because intolerances do not involve IgE antibodies and therefore do not show up on skin prick tests or specific IgE blood tests.
Hydrogen Breath Tests
Hydrogen and methane breath tests are the primary investigation for carbohydrate malabsorption, which underpins several common food intolerances. The most frequently ordered breath tests are for lactose intolerance and fructose malabsorption.
During a breath test, the patient drinks a solution containing a specific sugar (lactose or fructose) after an overnight fast. Breath samples are then collected at regular intervals over two to three hours. If the sugar is not properly absorbed in the small intestine, gut bacteria ferment it in the large intestine, producing hydrogen and methane gases that are absorbed into the bloodstream and exhaled through the lungs. Elevated levels of these gases indicate malabsorption.
Breath tests are available through most pathology providers in Australia and can be ordered by a GP. Medicare rebates generally apply when the test is clinically indicated.
Elimination Diets
For intolerances involving food chemicals such as salicylates, amines, and glutamates, there is no reliable blood test or breath test. The diagnostic approach is a structured elimination diet, ideally supervised by a GP and an accredited practising dietitian.
The Royal Prince Alfred Hospital (RPAH) Allergy Unit in Sydney has developed the most widely used elimination diet protocol in Australia, sometimes referred to as the RPAH Elimination Diet or the Friendly Food approach. The process involves removing suspected trigger chemicals from the diet for a defined period (usually two to four weeks), monitoring symptoms, and then systematically reintroducing individual food chemicals one at a time under clinical supervision to identify specific triggers.
This is a methodical process and not something to undertake casually. Unsupervised elimination diets carry a risk of nutritional inadequacy, particularly if they are overly restrictive or maintained for longer than necessary. A dietitian experienced in food chemical sensitivity can help ensure the diet remains nutritionally balanced throughout the investigation.
Coeliac Disease Screening
It is important to mention coeliac disease in any discussion of food-related symptoms, because it is frequently confused with wheat intolerance or wheat allergy. Coeliac disease is an autoimmune condition in which the immune system reacts to gluten, a protein found in wheat, barley, rye, and oats (in some cases). It causes damage to the lining of the small intestine and can lead to malabsorption of nutrients.
Coeliac Australia estimates that approximately 1 in 70 Australians have coeliac disease, though around 80 per cent remain undiagnosed. Screening involves a blood test for specific antibodies (tissue transglutaminase IgA, or tTG-IgA), followed by a small bowel biopsy to confirm the diagnosis. It is essential that the patient is still eating gluten at the time of testing, as removing gluten beforehand can produce a false-negative result.
A GP can order coeliac serology as part of an initial workup when a patient presents with symptoms such as bloating, diarrhoea, fatigue, or unexplained weight loss.
Receiving a diagnosis of a food allergy or intolerance is the beginning of a management journey, not the end of the investigation. What happens next depends on the nature and severity of the condition.
After a Food Allergy Diagnosis
For confirmed IgE-mediated food allergies, the primary management strategy is strict avoidance of the trigger food. This sounds straightforward but requires considerable vigilance, particularly for allergens that appear in processed foods under various names. ASCIA provides detailed information sheets and action plans that outline how to read food labels, manage cross-contamination risks, and respond to accidental exposure.
For patients at risk of anaphylaxis, a GP or allergist will prescribe an adrenaline autoinjector and develop a personalised ASCIA Action Plan for Anaphylaxis. Training on how to use the autoinjector is an essential part of this process, and refresher training should be revisited regularly.
Referral to an allergist or immunologist is recommended for anyone with a confirmed or suspected food allergy, particularly if the reaction was severe, if multiple food allergies are present, or if the patient is a young child who may benefit from monitored introduction or oral immunotherapy (desensitisation) programs.
After a Food Intolerance Diagnosis
Management of food intolerance typically involves identifying the threshold at which symptoms occur and adjusting the diet accordingly, rather than complete avoidance. Many people with lactose intolerance, for example, can tolerate small amounts of dairy, particularly fermented products such as yoghurt and aged cheeses.
Working with a dietitian is particularly valuable at this stage. The goal is to maintain as varied and nutritionally complete a diet as possible while managing symptoms effectively. Overly restrictive diets can lead to nutritional gaps and may negatively affect gut microbiome diversity, which is increasingly recognised as important for overall health.
For lactose intolerance specifically, lactase enzyme supplements taken with dairy-containing meals may help reduce symptoms. For fructose malabsorption, dietary guidance from a dietitian experienced in FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) can be particularly helpful, as fructose is one of the FODMAP subgroups.
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