Food allergies occur when the body's immune system (the body's own defense mechanism) responds abnormally to certain foods. Usually, the immune system helps the body to fight off harmful things like pathogens. For people with food allergies, the immune system incorrectly identifies certain food components as harmful and produces an inappropriate response. This leads to the unpleasant, and sometimes life-threatening, signs and symptoms associated with allergies.
More than 120 foods are known to cause food allergies. Cow’s milk protein allergy (CMPA), also known as cow’s milk allergy (CMA), is one of the most common food allergies in babies, and usually appears before 1 year of age.
Sometimes CMPA is confused with lactose intolerance, but they are very different: lactose intolerance does not involve the body's immune system. The two share some signs and symptoms, such as stomach and gut problems (like wind and diarrhea). However, while CMPA usually occurs in babies younger than 1 year old, lactose intolerance is very rare in children under 5 years of age.