Food intolerance

Possible signs of an intolerance include diarrhoea, abdominal pain and flatulence.

Bread roll with soft cheese

The term, food intolerances, covers a range of non-allergic reactions to food. The most common triggers are milk sugar (lactose), fruit sugar (fructose), gluten and histamine. Intolerances are usually due to impaired bowel function, i.e. the food is not digested properly. Unlike food allergies, intolerances are not life-threatening.


In a food intolerance, the body has partially or totally lost the ability to digest a certain substance – or has never been able to do so. There may also be an imbalance between the supply and degradation of a certain substance. In contrast to an allergy – with the exception of coeliac disease – the immune system is not involved in an intolerance.


The symptoms of a food intolerance can be many and varied. Most commonly, these are general digestive complaints, such as abdominal pain and cramping, flatulence, diarrhoea or constipation, increased bowel sounds and gas production, reflux, nausea, and vomiting. Other possible symptoms are headache, skin rashes and fatigue.


Intolerances are difficult to confirm. The diagnosis is based on medical history. Lactose and fructose intolerance are confirmed by means of an H2 breath test. The diagnosis of coeliac disease is based on the presence of specific antibodies in the blood and on colonoscopy.

As there is no specific test for histamine intolerance, an elimination diet (diagnostic diet) is followed with the support of a specialist dietitian.


After diagnosis, it is essential to eliminate any symptom-causing foods from the diet. As in lactose, fructose and histamine intolerance, small amounts are usually still tolerated, the individual tolerance level is determined in consultation with a specialist dietitian. In coeliac disease, a strict gluten-free diet must be followed all life long.

In terms of medication, the enzyme lactase can be taken as a tablet for lactose intolerance and the enzyme diamine oxidase for histamine intolerance.

Tips and tricks

  • always read the list of ingredients and, if present, any [allergen]-free information
  • ask in shops for special products
  • check the list of ingredients again at home for the products used before preparing food
  • the Allergy Seal of Quality provides good guidance and products that are suitable for people with intolerances can be found at
  • further, more specific advice for individual intolerances can be found under the respective heading.

Facts and figures

Approx. 20% of the Swiss population suffer from an intolerance.

Editors: aha! Swiss Allergy Centre in co-operation with the Scientific Advisory Board.