There’s no single “best” formula for every gassy baby, but partially hydrolyzed formulas are the most commonly recommended starting point. These formulas contain cow’s milk proteins that have been broken down into smaller pieces, making them easier for an immature digestive system to process. The right choice depends on what’s actually causing your baby’s gas, which can range from normal newborn digestion to a sensitivity to specific proteins or sugars in standard formula.
How Partially Hydrolyzed Formulas Work
Standard infant formula contains intact cow’s milk proteins, primarily whey and casein. Your baby’s digestive system has to do all the work of breaking those large proteins down into pieces small enough to absorb. When that process is slow or incomplete, bacteria in the lower gut ferment the undigested protein, producing gas.
Partially hydrolyzed formulas do some of that breaking-down work before the formula ever reaches your baby. The proteins are pre-split into smaller fragments called peptides. Research shows that hydrolyzed whey proteins are digested faster and more completely than intact proteins, because pancreatic enzymes and bile can act on the smaller pieces more efficiently. The result is less undigested material sitting in the gut and less gas production. Products in this category are often labeled “gentle” or “comfort” and are widely available without a prescription.
Extensively Hydrolyzed and Amino Acid Formulas
If a gentle formula doesn’t help after a couple of weeks, your baby’s gas may stem from an actual sensitivity or allergy to cow’s milk protein rather than simple digestive immaturity. Extensively hydrolyzed formulas (sometimes called hypoallergenic or elemental formulas) break proteins down even further, into very small peptides or individual amino acids. As the degree of hydrolysis increases, the allergenic potential of the proteins drops significantly.
These formulas are typically recommended by a pediatrician rather than chosen off the shelf, and they cost more. But for babies with a true cow’s milk protein allergy, they can make a dramatic difference in gas, fussiness, and stool changes. Amino acid-based formulas go one step further by eliminating intact protein chains entirely, and are reserved for the most severe cases.
Lactose-Reduced and Lactose-Free Options
Lactose is the natural sugar in breast milk and most standard formulas. True lactose intolerance is rare in infants, but some babies do seem to tolerate formula better when the lactose content is reduced. Lactose-free formulas replace lactose with other sugars like glucose or sucrose.
One thing worth knowing: many “sensitive” formulas swap lactose for corn syrup solids. While this can reduce gas symptoms in the short term, research from the NIH has linked early exposure to corn syrup solids in formula with changes in eating behavior later in childhood, including increased food fussiness and reduced enjoyment of food. The displacement of lactose may also affect gut microbiome development and appetite-regulating hormones. This doesn’t mean you should avoid these formulas if your baby genuinely needs them, but it’s worth trying a partially hydrolyzed formula with reduced (not eliminated) lactose first, and discussing the tradeoffs with your pediatrician if you’re considering a full switch.
Soy Formula
Soy-based formulas replace cow’s milk protein entirely with soy protein. Some families choose soy for dietary or cultural reasons. For gas specifically, soy formula can help if the problem is a reaction to cow’s milk protein, but it’s not a universal fix. A significant percentage of babies who react to cow’s milk protein also react to soy protein, so soy isn’t always the escape hatch parents hope for. Soy formula is lactose-free, which may help the subset of babies whose gas is related to lactose digestion.
What About Probiotic Formulas?
Some formulas now include added probiotics, and you can also buy infant probiotic drops separately. The most studied strain for infant gas and colic is Lactobacillus reuteri DSM17938. A meta-analysis of four double-blind trials found that infants receiving this probiotic cried and fussed about 25 fewer minutes per day compared to placebo by day 21, and were almost twice as likely to show meaningful improvement.
There’s an important caveat: those benefits were dramatic in breastfed infants but not significant in formula-fed infants. The reason isn’t entirely clear, but it may relate to differences in the gut environment. If your baby is formula-fed, a probiotic supplement is unlikely to hurt, but don’t expect it to solve the problem on its own.
How to Tell If Gas Is Something More Serious
Most infant gas is a normal part of a digestive system that’s still maturing. Babies swallow air when they feed and cry, and their gut bacteria are still establishing themselves. Some degree of gassiness is expected in nearly every newborn.
The symptoms that suggest something beyond normal gas include: blood or mucus in the stool, persistent vomiting (not just spit-up), poor weight gain, skin rashes like eczema appearing alongside digestive symptoms, or extreme inconsolable crying lasting more than three hours a day for more than three days a week. These patterns can point toward cow’s milk protein allergy or gastroesophageal reflux disease, though distinguishing between the two is genuinely difficult even for clinicians because the symptoms overlap so heavily. Regurgitation, crying, fussiness, poor appetite, and sleep problems show up in both conditions and in normal functional digestive discomfort.
If your baby is gaining weight normally, has no blood in the stool, and is generally content between fussy episodes, the gas is almost certainly within the normal range and a formula adjustment may be all that’s needed.
How Long to Wait After Switching
When you switch to a new formula, expect a brief adjustment period. Some increase in burping, gas, or changes in stool color and consistency is normal during the first few days as your baby’s gut adapts. Most pediatricians recommend giving a new formula at least one to two weeks before deciding whether it’s working. Switching too quickly, or cycling through multiple formulas in rapid succession, makes it impossible to tell what’s actually helping.
If you’re moving from a standard formula to a hydrolyzed one, some parents notice improvement within a few days. For cow’s milk protein allergy, it can take up to two weeks for symptoms to fully resolve after removing the offending protein.
Preparation Tips That Reduce Gas
Sometimes the issue isn’t the formula itself but how it’s prepared and delivered. A few practical adjustments can make a noticeable difference:
- Stir instead of shaking. Shaking a bottle creates air bubbles trapped throughout the liquid. Stirring with a fork or using a formula mixing pitcher introduces less air. If you do shake, let the bottle sit for a minute or two before feeding so bubbles can rise to the surface.
- Try ready-to-feed formula. Pre-mixed liquid formula has far fewer air bubbles than powder you reconstitute at home. It costs more, but it’s a useful test: if your baby’s gas improves on ready-to-feed, the problem may be air in the bottle rather than the formula’s ingredients.
- Use a slow-flow nipple. A nipple with too fast a flow forces your baby to gulp, swallowing more air with each sip. Newborns generally do best on the slowest flow available.
- Keep the bottle angled. Tilt the bottle so milk completely fills the nipple during feeding. If the nipple is half-empty, your baby is drinking half air.
- Burp mid-feed. Pausing halfway through a bottle to burp releases swallowed air before it moves into the intestines, where it causes discomfort.
A Practical Starting Approach
For most gassy babies without signs of allergy, starting with a partially hydrolyzed “gentle” formula is a reasonable first step. These are affordable, widely available, and effective for the most common cause of formula-related gas: immature protein digestion. If two weeks on a gentle formula doesn’t improve things, a lactose-reduced version of the same type is the logical next move. Beyond that, an extensively hydrolyzed or amino acid formula may be warranted, but that’s a conversation to have with your pediatrician, since those formulas are designed for diagnosed protein allergies rather than general fussiness.
In many cases, the combination of the right formula and better bottle technique resolves the problem entirely. Infant gas peaks around 6 to 8 weeks of age and typically improves substantially by 3 to 4 months as the digestive system matures.