When does lactose intolerance usually make itself known to a person?
Dr. Paige: In North Americans, it begins to surface around ages 8 to 12, when gas or looser stools begin to be associated with milk consumption. But it is not a smooth linear decline: the adverse reaction to milk will vary with how much milk is consumed, with other foods that are eaten along with milk, and with how much lactase is still being produced in the intestine.
