Cow's milk protein allergy is defined as an allergic reaction by the body's immune system to the proteins found in cow's milk. It is similar to a lactose intolerance reaction, but since it involves the immune system can cause other symptoms as well.
It can cause colic-like symptoms as well as vomiting, diarrhea, eczema, constipation,wheezing, and hives. Cow’s milk protein allergy is the most common food allergy an infant can have, but only affects 2-7% of infants. A small percentage of babies with cow’s milk protein allergy will also react negatively to soy. It would not help to switch to a lactose-free formula if your baby has a cow milk protein allergy. Consult a pediatrician to know whether your baby has a cow's milk protein allergy or is lactose intolerant.