Whereas one response is excessive, the other is insufficient. Both physical reactions from allergy or intolerance are easy to distinguish.

With allergies, the immune system reacts

A food allergy is defined as an overreaction of the immune system to harmless ingredients, mostly proteins, in foods. Common symptoms include vomiting, gastrointestinal problems, skin reactions, asthma or in extreme cases, anaphylactic shock. Adults are most frequently allergic to hazelnuts and walnuts, celery, apples and kiwi fruit. Reactions to hazelnuts, seafood or sesame are severe for the most part. Children typically react to cow’s milk, chicken eggs, wheat, hazelnuts and nuts or fish.

A food allergy is diagnosed by self-observation and also on the basis of skin and blood tests. The allergy-triggering substances, even in the tiniest amounts as for instance in spice mixes, must often strictly be omitted accordingly.

With intolerances, the digestion is affected

In the case of food intolerance, the immune system is not involved in most instances. The body is unable to digest a certain substance. It promptly reacts with ailments. Lactose intolerance and coeliac disease (gluten intolerance) are the most common.

With lactose intolerance, the body does not produce the digestive enzyme lactase or too little of it. In the case of coeliac disease, the mucous membrane of the small intestine is damaged by gluten (contained in various types of grain).


Editors: aha! Swiss Allergy Centre in co-operation with the Scientific Advisory Board. For prevalence figures, see source references.