Sometimes switching formulations -- say, from powder to concentrate, but not the brand -- can help, because your baby might be gassy from the bubbles that form when you mix the formula. Typically, your doctor will recommend a new formula only if your child shows signs that she may be allergic or intolerant to the proteins in milk. Besides fussiness after feedings, signs of either of these conditions include blood in your baby's stool and vomiting or diarrhea. Babies with a milk protein allergy can also experience hives and respiratory problems. If you're concerned, consult your child's doctor, who may recommend a hypoallergenic formula, which has cow's-milk proteins that are broken down enough to avoid causing a reaction in most babies. She may also test baby's poop for blood you can't see. --Gina Bevinetto Feld
Originally published in American Baby magazine, October 2007. Updated 2009.