Cow’s milk is one of the most common allergy-causing foods in children, and it’s the leading cause of allergic reactions in very young children. Milk allergy affects about 2 percent to 3 percent of infants worldwide, and its signs and symptoms can be serious enough to cause distress not just for an allergic child, but also for the child’s family. Most children outgrow a milk allergy by age 2 or 3. It’s important to differentiate a true milk allergy from milk protein intolerance or lactose intolerance. Unlike a milk allergy, intolerance doesn’t involve the immune system. Milk intolerance causes different symptoms and requires different treatment than does a true milk allergy. Common signs and symptoms of milk protein or lactose intolerance include digestive problems, such as bloating, gas or diarrhea, after consuming milk.