If you drink or eat dairy products and are breastfeeding, the cow's milk protein is passed to your baby. Cow's milk protein is also an ingredient in most infant formulas. Some babies are allergic to this protein.

Signs of cow's milk protein allergy include:

• Hives.
• Swelling of the face, tongue, mouth, or throat.
• Difficulty breathing, wheezing, or asthma.
• Abdominal (belly) pain.
• Vomiting.
• Diarrhea.
• Blood in the stools.

A formula-fed baby with a cow's milk protein allergy usually will be switched to a different kind of formula.

If your baby has signs of a milk protein allergy, contact your baby's doctor.