Lactose intolerance is a condition in which people have difficulty digesting lactose, a type of sugar found in milk and other dairy products.
Symptoms of lactose intolerance include abdominal pain, bloating, gas, diarrhea, and nausea. People with lactose intolerance are unable to fully break down lactose into glucose and galactose, and as a result, lactose is fermented by gut bacteria, producing gas and other digestive symptoms.
Lactose intolerance is caused by a deficiency of the enzyme lactase, which is needed to break down lactose.
Lactase production typically declines after childhood, but some people are born with congenital lactase deficiency, which is a condition in which lactase production is never normal.
Lactose intolerance is not the same as a milk allergy, which is an immune reaction to one or more proteins found in milk. Milk allergies can cause a variety of symptoms, including hives, wheezing, and vomiting.
Lactose intolerance can be managed by avoiding dairy products or by taking lactase enzyme supplements before consuming dairy products.
Some people with lactose intolerance can tolerate small amounts of dairy, while others may need to avoid dairy entirely.