Milk, quark, butter, Feta - Lactose intolerance - aha! Swiss Allergy Centre - Info on allergies © Image: photocrew  / Fotolia_30539376_XS@nt/fotoliaIn lactose intolerance the digestive enzyme lactase is not produced or only in insufficient quantities. This leads to flatulence, diarrhoea or stomach pains. The enzyme is necessary to break down lactose (milk sugar) into its constituents. In Switzerland roughly one in five people suffers from lactose intolerance.

Causes and triggers

Milk sugar (lactose) is a disaccharide, comprising galactose and glucose. Lactose is found naturally in the milk of mammals. Small amounts of lactose are added to foods but are also used in industrial production as well as finished products, seasoning mixes or medicines.

In normal circumstances, lactose is split into its two constituents by the enzyme lactase in the small intestine because this is the only way they can be absorbed via the intestine into the blood. If a lactase deficiency exists because of a hereditary condition or due to some other disease, we refer to a lactose intolerance. Instead of reaching the blood, lactose gets into the large intestine undigested where it is fermented by bacteria.


The gases formed in the large intestine and the accumulation of water lead to the typical symptoms, such as flatulence, stomach cramps, diarrhoea, nausea, wind, constipation and vomiting. Lactose intolerance does not result in a life-threatening situation. However, it can be very unpleasant and inhibiting for sufferers.

Diagnosis and differential diagnosis

Sufferers often notice that they do not tolerate milk and dairy products well and observe typical symptoms of lactose intolerance. It can be helpful for the doctor if the sufferer records what foods he has eaten and what symptoms he has observed in a food and symptom diary.

The H2 breath test and a genetic blood test provide reliable methods for confirming the diagnosis or differential diagnosis.

Other food intolerances like fructose malabsorbtion and coeliac disease  trigger similar symptoms. In babies and infants, an allergic reaction to milk protein might also be responsible for the symptoms.

Treatment / Therapy

The treatment of lactose intolerance takes the form of a low-lactose diet. As far as possible, sufferers should follow a lactose-free diet for a short time after being diagnosed. Their individual tolerance of lactose is then determined in a subsequent test phase. Individual dietary recommendations can be put together with a professional (e.g. nutritionist).
Taking the deficient enzyme lactase in capsule or tablet form is a possibility.

Tips and tricks

  • As a rule, lactose is absorbed more effectively if foods rich in fats or protein are eaten at the same time.
  • Small quantities of foods containing lactose, distributed throughout the day, are usually well tolerated.
  • Mature cheese is often well tolerated because most of the lactose is broken down by bacteria during the maturation process.
  • A large number of lactose-free specialist products are available from retailers and specialist shops.

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


aha! Swiss Allergy Centre helps

  • aha! keeps a list of HF/FH certified and experienced nutritionists who have qualified and recognized training and have completed advanced training on the subject of food allergies and intolerances. Nutritionists
  • aha!shop: Booklets and factsheets provides detailed information and are available in German, French, Italian.  The booklet "Allergies – simple to explain" and the questionnaire "Do I have an allergy" is available in English
  • Experts on the aha!infoline will be happy to answer personal queries: Monday to Friday, 08.30–12.00.
  • Products and services awarded the Swiss Allergy Label – an added benefit for sufferers.
  • aha!kinderlager for children with allergies aged between 8 and 12 years: holidays full of variety with lots of sports, play and fitness. Under expert supervision, children learn to deal better with their allergies and/or asthma.
  • aha!jugendcamp for youngsters aged between 13 and 16 years: a broad range of sports and leisure activities, skilled leaders tackle aspects of allergic diseases in adolescence.
  • Education and courses on the subjects "Allergy, asthma, chronic bronchitis", "Anaphylaxis" and "Neurodermatitis"
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