Allergies aren’t the first thing that jump to mind when formula-fed babies are having health problems or seem fussier than usual - they’re not even eating real food yet, so what do they have to be allergic to? Unfortunately, the cow’s milk that makes up the base of most formulas is one of the most common food allergens. It's rare for very young babies to have food allergies, since most food allergies emerge later in life, but about 2% to 3% of infants do have milk allergies, so it can be helpful to know what to watch out for.
Babies who haven’t been introduced to solids yet but are having some trouble with what they’re ingesting are much more likely to have an allergy than an intolerance (although a lactose intolerance is still possible, especially for babies with family histories of lactose intolerance), which means that rather than just having trouble digesting certain parts of what they’re eating, their bodies actually react negatively against certain proteins or compounds.
Allergy symptoms include:
Most babies who experience allergic reactions while formula-feeding and before solids have been introduced are allergic to dairy. Unfortunately, an allergy to milk proteins, which is what most dairy allergies are, often overlaps with soy allergies. Babies who continue to have allergic reactions after both milk and soy proteins have been removed from their diets might also have an allergy to corn. The vast majority of formula brands use some corn products, though there are a few corn-free brands.
If you suspect your child might be having an allergic reaction to her formula, it’s definitely time to talk to a pediatrician. Since allergy symptoms can seem like other health issues - particularly colic - it’s a good idea to take careful note of the timing and pattern of any symptoms you notice in the days leading up to an appointment. A pediatrician may recommend switching formulas, speaking to an allergist, or both.
Though soy-based formula is a good alternative to cow’s milk-based formula for many babies who have trouble digesting milk, it doesn’t work for all babies with allergies. Some of the proteins in soy are not too different from milk proteins, and so babies who can’t process milk proteins may also have trouble processing soy proteins. Formula-fed babies who have trouble with both milk and soy proteins are generally transitioned back to a milk-based formula, but one that is either hypoallergenic or amino acid-based.
Formulas designed for sensitive stomachs generally aren’t different enough from regular formula to make a difference for babies with allergies or serious intolerances. Hypoallergenic formulas are much more likely to work, but in cases where they don’t, a pediatrician may prescribe an amino acid-based formula, which is not available over the counter.
After switching formulas, parents generally start to see results within 48 hours.
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