How Changing Formula Effects an Infant
During the first year of life, babies drink hundreds of bottles of formula -- usually the same formula. At times, though, a baby's formula needs to be changed due to allergies or costs. It is usually safe to switch brands of the same type of formula, but before you make any changes to your child's nutrition, check with your pediatrician. Once you've made the change, you'll need to pay attention to signals from your baby in case an ingredient or nutrient in the new formula causes a problem for your infant.
Switching for Allergies
Sometimes allergies necessitate a switch in formula, but unfortunately the new formula can also cause allergies. For instance, lactose-intolerant babies are often switched to a soy-based formula. Some babies are also allergic to soy, so parents may see continuing allergy symptoms because of that. Look for reactions, such as fussiness, diarrhea or gas soon after feedings as symptoms of an allergy recommends KidsHealth. Consult your pediatrician for direction, though, as sometimes it takes a little while for a baby's digestive tract to adjust to a new formula, and it may not be an allergy causing the problem.
The Taste Challenge
It's possible that your baby simply won't like the taste of the new formula, and a baby who doesn't like what's in the bottle isn't going to want to finish his meals. This refusal to feed can lead to inadequate nutrition. Note how much formula your baby is drinking prior to the switch, and then compare it to what he's eating a week or so after the switch. If he is still gaining weight and is generally happy, the new formula is not affecting him adversely.
Colic or Gas
Changing a baby's formula won't usually cause (or cure) colic, but it can cause your baby to have excess gas or bloating. An allergy can occasionally cause gas, according to KidsHealth, but simply switching a baby's meals to a formula with different ingredients or additives can also cause it. An infant's digestive tract is immature and sensitive to any changes and a change in formula, especially to one that is fortified with iron, can cause constipation, which in turn often causes gas.