People with lactose intolerance usually start to have a decrease in lactase production by the intestine by 3 to 6 years of age. But, the majority of people with lactose intolerance do not begin to get symptoms until the teen years or adulthood. Symptoms start between 30 minutes and two hours after the child eats or drinks a milk product and include:
- Crampy abdominal pain
Each child with lactose intolerance is different, and some experience more severe symptoms than others.