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Food intolerance: distinguishing it from food allergy

Food allergy and intolerance are not the same thing but they are both types of food sensitivity. When someone has a food allergy, their immune system over reacts, producing specific proteins called antibodies to ‘fight’ the problem food. This can lead to symptoms of an allergic reaction. This reaction may even be severe enough to cause a life-threatening condition called anaphylaxis

On the other hand, food intolerance doesn’t involve the immune system. It is predominantly a digestive system response that is related to the amount of a problem food that you eat. Although food intolerances are not generally life-threatening, they can make you feel very ill which is why they're sometimes confused with allergies.

So how do you tell the difference between food allergy and food intolerance?

Food intolerances don’t involve the immune system. They are often reactions triggered by food chemicals which irritate nerve endings in different parts of the body, similar to the way certain drugs cause side-effects in sensitive people.

Some people are more sensitive to food chemicals than others. This is usually a genetically-inherited problem, but environmental triggers, such as a sudden change of diet, a bad food or drug reaction, a viral infection such as gastroenteritis or glandular fever, can also trigger symptoms at any age by changing the way the body reacts to food chemicals. Babies are more vulnerable to food chemicals because their metabolism, gastrointestinal and nervous systems are immature. As children get older they become used to handling small amounts of rich, highly-flavoured foods, and these usually only cause problems if eaten in excess.

The natural chemicals in some healthy foods such as milk, mushrooms, tomatoes, oranges, strawberries and cheese can be just as much of a problem for sensitive people as those chemicals used as food additives.

Food intolerance can also be due to problems in the breakdown process of a food, or caused by some toxic property of the food.

Your healthcare provider can help determine if you have an allergy or intolerance, and establish a plan to help control symptoms.

Common symptoms of an allergic reaction

Some food allergies result in immediate, severe and even life-threatening symptoms, whereas others cause symptoms which may take longer to develop.

You may get some or all of the following symptoms:

  • Itching and/or swelling of your lips, mouth, tongue and throat
  • Constriction or tightening of your throat and airways
  • Wheezing or shortness of breath
  • Coughing
  • Runny nose
  • Sore, red and itchy eyes
  • Skin reactions (e.g. swelling and itching, hives, eczema and flushing)
  • Diarrhoea, feeling nauseous, vomiting and bloating of the stomach.

Foods that most commonly trigger food allergies include nuts (peanuts, Brazil nuts, almonds, hazelnuts, pistachios etc), eggs, milk, fish, shellfish, sesame seeds and wheat.

Common symptoms of food intolerance

The symptoms of food intolerance may include one or more of the following:

  • Nausea and vomiting
  • Stomach pain
  • Gas, cramps or bloating of the stomach
  • Heartburn
  • Diarrhoea
  • Headaches
  • Irritability or nervousness.

What should you do if you think you have a food intolerance?

Don’t self-diagnose a food intolerance and cut out certain foods without first seeking medical advice. Your symptoms could be masking a medical condition that may not be linked to food at all. See your doctor with any concerns as they can then refer you to a medical specialist, a hospital allergy clinic or an accredited practising dietitian who specialises in food intolerance.

Further information

Royal Prince Alfred Hospital Allergy Unit


Australasian Society of Clinical Immunology and Allergy (ASCIA). Diagnosis and management of food hypersensitivity in childhood. [online] Balgowlah, NSW: ASCIA; c2010 [updated Jan 2010, accessed 2 Aug 2010] Available from:

Swain AR, Soutter VL, Loblay RH. Food allergies and intolerances. In: Friendly Food. Sydney: Murdoch Books. 2006. [accessed 2 Aug 2010] Available from:

The Cleveland Clinic. Problem foods: is it an allergy or intolerance? [online] Cleveland, Ohio: The Cleveland Clinic Foundation; c1995-2010 [accessed 2 Aug 2010] Available from:

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This information has been developed and reviewed for Bupa by health professionals. To the best of their knowledge it is current and based on reputable sources of medical research. It should be used as a guide only and should not be relied upon as a substitute for professional medical or other health professional advice.

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Last published 31 October 2010