What is the difference between a food allergy and intolerance?

There is often a LOT of confusion around these two terms. All reactions involving foods are called ‘food hypersensitivity’ which includes food allergies as well as intolerances such as lactose intolerance and foods producing unpleasant symptoms, for example caffeine in coffee and cola, for some people.

Food allergies involve the immune system, whereas intolerances such as lactose intolerance are due to an enzyme deficiency (lactase in this case) resulting in undigested lactose to be fermented in the gut and producing gut symptoms such as abdominal pain, excessive wind and explosive diarrhoea.

Food allergies occur when the immune system – the body’s defence against infection – mistakenly treats proteins found in food as a threat. As a result, a number of chemicals are released and it is these chemicals that cause the symptoms of food allergies.

Symptoms of food allergies and food intolerances can be similar and often overlap, so this is where the confusion comes in. However, lactose intolerance does NOT result in any skin symptoms (swelling, redness, hives, worsening eczema) or respiratory symptoms ONLY gut symptoms and lactose intolerance also does NOT result in any blood or mucus in the stools (this can also occur after an infection or as a result of an allergy but does not occur with lactose intolerance).

Also with food intolerance, varying quantities of the food may be tolerated, so that the food does not need to be completely eliminated from the diet. Whereas with a food allergy, even small quantities of the food protein can trigger a reaction.

Please note: Some children with milk or egg allergies may tolerate baked forms of the proteins found in milk or egg but this would need to be established on an individual basis and may require a supervised oral food challenge in hospital or your allergy clinic may advise you to follow the milk or egg ladder (only for non-IgE mediated or delayed allergies) at home for reintroduction.

A food allergy can be immediate (a few minutes up to 2 hours after eating a food) or delayed (2 hours to 2 days after eating a food) in onset….


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