Lactose intolerance may resolve on its own in some babies after the age of three, while others may not recover from it. Lactose intolerance primarily occurs because the secretion of lactase in the intestines decreases, leading to incomplete breakdown of lactose found in breastmilk or cow's milk. This results in symptoms such as diarrhea, bloating, and indigestion. There are two causes of lactose intolerance: one is congenital lactose intolerance, which requires long-term medication or avoiding dairy products as much as possible. The other cause is transient lactose intolerance due to infection, which generally improves about a month after treatment.