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Lactose intolerance happens because the body has trouble digesting a kind of sugar. This sugar — called lactose — is in milk and milk products.

More to Know

Lactose intolerance happens when the body makes too little of an enzyme called lactase. The body needs lactase to break down lactose. 

People with lactose intolerance might have belly pain, gas, bloating, and diarrhea after they eat milk products. How bad these problems are depends on the person. Some people can have small amounts of dairy without problems. Others have a lot of stomach trouble and need to avoid all dairy products. 

Sometimes people get lactose intolerance after an illness or from taking medicines. In these cases, the lactose intolerance can go away after a few days or weeks.

Keep in Mind

People can manage lactose intolerance by not drinking as much milk or eating fewer dairy products. Because the body needs calcium, they should eat more non-dairy products that have calcium, like calcium-fortified juice or soy milk; green, leafy vegetables; and beans. People who avoid milk and dairy products may need calcium and vitamin D supplements. 

Taking lactase enzyme supplements before eating dairy will help the body digest lactose and prevent problems. 

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.