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Lactose intolerance: Overview

Last Update: February 2, 2012; Next update: 2015.


A bloated belly, "wind" or diarrhea are typical digestive symptoms that some people have after eating or drinking dairy products. People who have difficulty digesting dairy products may only tolerate certain amounts of lactose (milk sugar). This is called lactose intolerance. Some people who are over-sensitive to milk might actually have another problem. It is important to get the diagnosis right before deciding to make major changes to your diet, especially in children, teenagers and people who need more calcium.

Lactose intolerance is not an allergy. This is an important difference. People who have a true milk allergy can react to even a tiny amount of dairy foods or milk. But people who are lactose intolerant can actually consume quite a lot of these products without any problems.


Symptoms are normally noticed shortly after eating or drinking dairy products. The amount of lactose that causes symptoms varies from person to person. The symptoms can include:

  • A bloated belly
  • Pain in the lower abdomen
  • Increased flatulence ("gas" or "wind")


Babies' digestive systems are pre-programmed to only survive on breast milk. In order to digest milk, babies produce the enzyme lactase. This enzyme breaks down the milk sugar, or lactose, in the bowel so that the body can process it further. When a child is weaned off breast milk, the digestive system gradually adapts to processing other foods. The body then produces considerably less lactase, and can therefore only break down smaller amounts of lactose.

The amount of lactose an adult can digest varies. People with a lactose intolerance either have much less lactase or their bodies absorb lactose worse than people who still tolerate dairy products well as adults.


A diet or elimination test with a follow-up lactose tolerance test is carried out to diagnose lactose intolerance: For a certain time you are not allowed to consume milk or dairy products, and after that time you consume a certain amount of lactose.  The body's reaction to that is then monitored.

A breath test can also be carried out in which the hydrogen content of your breath is measured. It is normally higher in people who have a lactose intolerance.

Everyday life

There is no medical treatment for lactose intolerance. But it is possible to live a symptom-free life by following a special diet. Dairy products are not an essential part of a balanced diet.


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  • IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

    Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. We do not offer individual consultations.

    Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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