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Food Intolerance OR ALLERGY? 

Food Intolerance or food allergy? These terms are often used interchangeably which can be very confusing.


While there are also a lot of overlapping symptoms, there are some important differences due to the fact that allergy involves the immune system while food intolerance does not. 


  • There are 2 types of true allergies: one is IgE allergy which shows on on testing (skin price testing or blood tests), and the other is cell mediated allergies which do not show up up on testing

  • Symptoms can range from mild to severe with the most severe being anaphylaxis (associated with IgE allergies and rarely happens)

  • Symptoms of severe allergic reactions (anaphylaxis) affect breathing and/or our heart and may include: difficult/noisy breathing, swelling of tongue, swelling/tightness in throat, difficulty talking/hoarse voice, wheeze or persistent cough, persistent dizziness and/or collapse, and becoming pale and floppy in young children. 

  • IgE allergy symptoms typically start within minutes to 1 hour within eating or drinking the allergen and may include may include hives, itchiness, lip or tongue swelling, difficulty swallowing, throat tightening, chest tightness, trouble breathing, wheezing, and abrupt abdominal discomfort that may be associated with nausea, vomiting, and/or diarrhea.

  • ​Non IgE allergies (also called cell medicated allergies and T-cell mediated allergy) have a more delayed start of symptoms after eating or drinking the trigger allergen. Gut symptoms are more chronic than acute and may present as vomiting, diarrhoea, blood in the stool, and weight loss or poor growth. Examples of non IgE conditions include oeosinophiliac oesopaghitis, FPIES, (food protein induced enterocolitis syndrome), proctocolitis (blood in the stools), and enteropathy.

  • Symptoms found to be consistently reproduced by food ingestion

  • Food allergy is more common in people who have other allergies such as allergic rhinitis (hay fever), asthma or eczema.

More than 90% of food allergies are caused by the following protein foods: peanuts, tree nuts (eg macadamia), fish, shellfish, cow's milk, eggs, soy, wheat,  sesame and lupin. However, any food has the potential to be allergenic as all foods contain even small amounts of protein.

In Australia, the most common IgE food allergens are egg, peanut and cow's milk in children and tree nuts and seafood in adults.

The Food Standards Code requires these foods to be declared on labels whenever they are present as ingredients or as components of food additives or processing aids.

If you are have food symptoms (adult), chances are you are more likely to be suffering from food intolerances than a food allergy.

  • Up to 2% of adult Australians have foods allergies

  • It is thought that at least 10% of the population have intolerances.

If you have a food allergy as an adult then there is a 70% chance that you will also also suffer from food intolerances.

Allergies should be considered in babies or children with food symptoms. Allergies to milk, egg, wheat and soy are more common in  babies than older children and adults:

  • infants less than 12 months of age (10%)

  • children 1 - 5 years of age (4 - 8%) 

  • older children 10 - 14 years (5%)


Milk, egg and soy allergies commonly resolve with age. Most young children grow out of their milk allergies by the 3-5 years of age, with 85% grown out of it by the age of 5. Roughly 50% of children grown out of their egg allergy by the age of 6 years. Peanut, tree nut, sesame, fish and shell fish allergies usually persist.


  • ​Symptoms to offending foods are dose related. This means that trace or tiny amounts of the problem foods are unlikely to set off symptoms, and you will only react when there is a build-up in your system and your personal threshold is crossed

  • This means that a food may cause a problem one day but not cause a problem another day. This is very typical of food intolerance reactions.

  • Symptoms only subside when the chemicals are able to be broken down and removed from the body which can take from days to weeks.  Symptoms will not subside however if the offending food(s) continue to be eaten.

  • Reactions are usually not life threatening (rarely  for food chemical intolerance and never for FODMAPs) although you may feel very unwell

  • Headache, joint pain, and brain fog are not common symptoms of food allergy- point more to food intolerances

  • Does not show up on allergy testing

Food Allergy?

If you suspect a food allergy (especially in a child) then you need to see an Allergy or Immunology Medical Specialist. See your GP for a referral.

IgE allergies can be diagnosed through IgE blood tests (RAST tests) or skin prick tests (SPT) and oral food challenges which must be done under medical supervision due to the potential seriousness of the reactions. This is very important if you have life threatening or severe reactions. These tests are often carried out on adults and children but are less reliable with young babies.

Many people with positive allergy tests do not actually have an allergy. For this reason, it is really important that only trained medical professionals perform and interpret the test. 

Cell-mediated allergies  do not show up on any testing and their reactions tend to be more delayed. 


Treatment involves complete avoidance of the problem foods, as even minute amounts of the offending food can provoke reactions.

Allergies and food intolerance often co-exist. 

Food Intolerance?

Our knowledge of food intolerances is limited, despite food intolerances or sensitivities being more common than allergies. Consequently we do not yet understand the mechanism of food intolerances.


There are different types of food intolerances- including FODMAPs , food chemicals  and   whole foods and gluten intolerance. Note that gluten intolerance is different to Coeliac Disease which is a T cell mediated allergy.


Personal information data such as family history, types of foods thought to bring on reactions, types of symptoms  can indicate which is most likely. They often occur together.


It is advisable to check with your doctor to eliminate any other causes of your symptoms including Coeliac Disease. Think of checking for Coeliac Disease before gluten is eliminated as gluten needs to be in the diet at least 4-6 weeks prior to the tests. It can be hard to put it back in once removed from the diet.


No matter the current fad, there are no scientifically valid tests for food intolerances. A diet elimination or manipulation is the gold standard way of diagnosing food intolerances.

Click on the appropriate elimination diet to find out more: FODMAP or FOOD CHEMICAL elimination 


Based on your unique reaction profile, a properly constructed diagnostic diet is put together to match your individual dietary needs to help you identify what is causing your food symptoms. 


  1.  Lesley Clarke, Jenny McQueen, Ann Samild, Anne Swain. Dietitians Association of Australia review paper: The dietary management of food allergy and food intolerance in children and adults. Aust J Nutr Diet, 1996. 53: 89-98. Retrieved 2017-4-22.

  2. Australasian Society of Clinical Immunology and Allergy. (2016). Food Allergy. Retrieved 2017-3-9.

  3. Sicherer SH, Wood RA, Vickery BP, et al. The Natural History of Egg Allergy in an Observational Cohort. The Journal of allergy and clinical immunology. 2014;133(2):492-499.e8. doi:10.1016/j.jaci.2013.12.1041.

  4. Better Health Channel. Food Allergy and Intolerance. 2013-July. Retrieved from: 

  5. Retrieved on: 2017-4-22.

  6. Ascia. Information for Parents, Consumers and Carers. Food intolerance. 2014-Jan. Retrieved from: Retrieved on  2017-4-23.

  7. Anderson, J. Food-sensitive babies, dietary investigation for breastfed babies. 2017, Specialist Dietitian and Lactation Services.

  8. The Gastroenterologist's Guide to Food Allergies, Intolerances, and Sensitivities - Medscape - Apr 11, 2022.

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