Cow’s milk protein allergy is the most common allergy in infants, and routine infant formulas are milk-based and therefore a source of cow’s milk protein. That's why pediatricians often suggest a “hypoallergenic” formula for babies when they think they might have a cow’s milk protein allergy. Hypoallergenic formulas have proteins that are “hydrolyzed” or broken down into very small pieces. This process helps most babies with cow’s milk protein allergy tolerate the formula, and avoid reactions to the larger proteins from routine milk-based infant formula, including partially hydrolyzed milk-based formulas.
Formula-fed babies who switch to a hypoallergenic formula can expect to see symptoms improve within a few days. After 2 to 4 weeks, symptoms should disappear. However, if your baby has severe symptoms, more than one food allergy, or if their symptoms don’t improve on an extensively hydrolyzed formula, your doctor may switch them to an amino acid-based hypoallergenic formula.
Differences in special formulas
Be sure to work with your pediatrician when considering hypoallergenic formulas. There are two types: extensively hydrolyzed and amino acid formulas. The main difference is the form of “protein” in these formulas. Extensively hydrolyzed infant formulas are small chains of amino acids and amino acid formulas are made of only amino acids for the "protein" source.
If extensively hydrolyzed, hypoallergenic formulas don’t help your baby with cow’s milk protein allergy, her pediatrician might suggest switching to an amino acid-based formula to see if that works.