Lactose intolerance is caused by lactose malabsorption, a condition in which your small intestine makes low levels of lactase and can’t digest all the lactose you eat or drink. To diagnose lactose intolerance, your doctor will ask about your symptoms, family and medical history, and eating habits. Lactose intolerance occurs in people who lack the enzyme they need to break down lactose, the sugar in milk. It causes digestive distress when you eat dairy products. What is lactose intolerance? Lactose intolerance is a common cause of abdominal cramping, bloating, and loose stools. This condition occurs when the body does not have enough of the intestinal enzyme lactase. The job of lactase is to break down lactose, the main sugar in milk. Lactose intolerance is most common among people of East Asian descent (with 90% lactose intolerance), people of Jewish descent, people in African and Arab countries, and among some people of Southern European descent. Millions of Americans can’t digest a certain sugar in milk and milk products called lactose. If you’re one of them, you have lactose intolerance. The condition isn’t harmful, but it can be. Find out about lactose intolerance, what the symptoms are, what the treatments are, what tests can find out if you have it, and what causes it. Lactose intolerance is a condition that makes it hard to digest the sugar in milk and milk products, called lactose. People with lactose intolerance often have diarrhea, gas and bloating after eating or drinking foods containing lactose.