How do you find out if a baby is allergic to baby formula?

There are many signs that your baby may be allergic to a formula. In most cases babies are not "allergic" to the formula. But are either lactose intolerant or might have GERD. Gastroesphogael Reflux Disease. A good sign is diarrhea or bowels that have any kind of shape and/or form. Excessive crying. Projectile vomitting or even excessive spitting up. Not going through more than the usual amount of diapers and is suffering from dehydration. It is always best to consult your peditrician if you believe your baby might have an allergy or a health problem to a particular formula you might be using.