Food intolerance vs food allergy

Food allergies and intolerances have increased considerably in recent years and are therefore now well known to the general public. Broadly speaking at least. For when it comes down to knowing how they work or explaining what distinguishes these two conditions, things get more complicated and there tends to be a certain amount of confusion. Spotlight.

Intolerances and allergies: what is the difference?

The key difference between food intolerances and food allergies has to do with the mechanism that is activated in the body following the ingestion of the food causing the disorder. A food allergy is an immunological reaction, which means that the ingested food triggers a reaction from the immune system. Conversely, a food intolerance does not involve the immune system (IgE), but another mechanism; to this day, many of these mechanisms are not fully understood.

A food allergy always involves a protein contained in a food, or a component of that protein. The immune system, which is our body’s basic defence system, identifies this (animal or plant) protein as dangerous, when in reality it is harmless. Most of the time, the body then produces antibodies called immunoglobin E (IgE) to attack the allergens in question. A whole series of symptoms ensues, of varying speed and intensity, the most violent of which may lead to death.

In contrast, the symptoms of a food intolerance have more to do with the digestive system. They often result from its inability to digest or absorb certain foods. In the case of lactose intolerance for example, the body is unable to digest lactose – the sugar found in milk – due to a lack of lactase (the enzyme that hydrolyzes lactose to allow it to be absorbed).

Because they activate the immune system, food allergies can be diagnosed through laboratory tests. The diagnosis is less straightforward for food intolerances and is often based on symptomatology (i.e. on the analysis of all the symptoms), which is why the very existence of certain food intolerances is sometimes disputed.


Main source: Revue Médicale Suisse, 2014; 10 : 846-53. Allergie ou intolérance alimentaire ?

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