Cows milk protein allergy (CMPA), also known as cows milk allergy (CMA), is one of the most common food allergies in babies, and usually appears before 1 year of age. CMPA is a type of milk allergy where a babys immune system responds to the proteins found in cows milk, causing the baby to have allergic symptoms.Milk allergy is the result of an immediate autoallergic reaction in cattle that are sensitized to their own casein. ?-lactalbumin and ?-lactoglobulin are the most important allergens.