Food allergies, food intolerance and anaphylaxis – what’s the difference?

Living with a food allergy is challenging – just ask the one in 10 infants and two in 100 adults who are thought to be affected across Australia.

Foods that are the most common causes of food allergies include cow’s milk, eggs, tree nuts, peanuts, fish, shellfish, soy, eggs, and wheat. Other foods that can cause a severe allergic reaction include kiwi fruit, chicken, mustard, celery, and banana.

Unlike food intolerances, food allergies happen when your immune system mistakes some of the proteins in food as being harmful. This can then cause potentially life-threatening reactions, so the only treatment is to remove the food from your diet.

Most of the time, food allergies in children are not severe, and they may outgrow them.  However, nut and seafood allergies may persist.

Signs of an allergic reaction

When your body mistakes a food protein for being something harmful (an invader) the immune system reaction can affect your skin, heart, breathing or gastrointestinal tract. The reactions usually happen within 20 minutes of eating.

Symptoms of a mild allergy can include hives on the skin, swelling on the face or mouth, vomiting or abdominal pain or discomfort.

A severe allergy may include:

  • Wheezing or breathing troubles
  • Difficulty talking and a hoarse voice
  • Coughing
  • Swelling or tightness of the throat
  • Collapsing
  • Light-headedness or dizziness
  • Diarrhoea
  • Swelling of the tongue
  • Young children may go pale and floppy.

If left untreated, an allergic reaction can become life-threatening quickly.

Treatment of severe allergic reactions

Anaphylaxis is the state the body enters into when an allergic reaction involves more than one body system (for example, skin, respiratory, gastrointestinal, cardiovascular) and this should be treated as a medical emergency. Call triple zero (000) immediately and lay the person down. If they have an adrenaline injector and you can administer it then do so.

Allergy & Anaphylaxis Australia has more information about what to do in an emergency, including tips on how to support the person having a reaction, and what to inform emergency services.

Tests for food allergies

Skin or blood tests can be used to find triggers for a food allergy, and sometimes health professionals recommend a temporary elimination diet to try and identify the cause.

Treatment and what to do

Food allergies are managed under the guidance of a clinical immunologist or allergy specialist. Mostly, the person with the allergy must avoid the food they are allergic to. This is a considerable effort on their part, meaning they must read food labels carefully, avoid cross contamination when preparing food and be careful about eating out.

They will always need to have their adrenaline autoinjector and action plan for anaphylaxis with them, so they know what to do when a reaction happens.

The difference with food intolerances

Food intolerances are sometimes confused as food allergies, but they are not the same.

Food intolerance is a broad term used to describe a wide range of adverse reactions to foods, that cause symptoms after eating some foods. According to the Australasian Society of Clinical Immunology (ASCIA) these include stomach pain, bloating, gas/flatulence, diarrhoea, irritable bowel syndrome (IBS), rashes, hives (urticaria), recurrent mouth ulcers or headaches.

Food intolerances involve the digestive system, while food allergies involve the immune system. While they generally don’t cause severe or life-threatening reactions in people, if food intolerances are not properly managed, these symptoms can adversely affect a person’s general health and wellbeing.

Food intolerances can include:

  • Metabolic conditions, such as lactose intolerance and carbohydrate malabsorption.
  • Chemical sensitivity reactions to caffeine, monosodium glutamate (MSG) and naturally occurring food chemicals such as salicylates and amines.
  • Toxic reactions like food poisoning or scombroid (or histamine) fish toxin.
  • Adverse reactions to artificial preservatives. Sulphites (often found in dried fruit, drinks like wine, beer, fruit juices and medications), and benzoates (often in soft drinks) can cause symptoms in some people. These preservatives have also been reported as triggers for asthma, and in rare cases triggers for anaphylaxis. 
  • Reactions to natural substances. Caffeine and curry are gut irritants that can trigger indigestion.  Vasoactive amines such as tyramine, serotonin and histamine are also known triggers of migraines or nasal congestion in some people. Vasoactive amines occur naturally in pineapples, bananas, baked meat, avocados, chocolate, vegetables, some wines, citrus fruits, and mature cheese, among others.
  • For more information about food intolerances, including natural and chemical reactions visit ACSIA’s webpage on food intolerances.

Diagnosing food intolerances

Food intolerances can often be difficult to diagnose but once a diagnosis is made, it will be helpful to know how to manage your diet and identify factors that could make your symptoms worse. In making a diagnosis a GP will look at your clinical history, response to treatment and testing. He or she will also check for other conditions that could be causing symptoms. An elimination diet – where certain foods are removed then reintroduced later when testing for symptoms – may also be considered.

Irritable bowel syndrome

Sometimes irritable bowel syndrome (IBS) can be confused with food allergies, as it is a common condition that affects the large intestine. Signs and symptoms include cramping, bloating, gas, abdominal pain and diarrhea or constipation, or a combination of both. Triggers for IBS can include food and stress, though the exact cause of IBS isn’t known. Factors that could play a role include weak muscle contractions in the intestine, abnormalities in the nerves of the digestive system, a surplus of bacteria in the intestines, early life stress or changes in gut microbes.

Talk to your GP about this to determine the best way of identifying and managing issues associated with your gastrointestinal health.

  • The Mayo Clinic has some more information about IBS, including the causes and symptoms. 

Sources and for further information: