Lactose intolerance is when someone has trouble digesting lactose, a sugar found in milk, and other dairy foods. If people with lactose intolerance eat dairy products, the lactose from these foods passes into their intestines, which can lead to gas, cramps, a bloated feeling, and diarrhea. Some people can have small amounts of dairy without problems. Others have a lot of stomach trouble and void all dairy products. Many foods, drinks, and digestive aids are available to help manage lactose intolerance eat something containing lactose, and an enzyme in the small intestine called lactase breaks it down into simpler sugar forms called glucose and galactose. These simple sugars are then absorbed into the bloodstream and turned into energy body doesn't make enough lactase to break down lactose. Instead, undigested lactose sits in the gut and gets broken down by bacteria, causing gas, bloating stomach cramps, and diarrhea.