Why Does Baby Spit Up Breast Milk But Not Formula?

As a parent of a little one, one thing you quickly become accustomed to is the constant hum of the laundry machine as you go about your day.

The washing machine will be working overtime for the first few months of your little one’s life!

You will be removing spit-up from their burp cloths and onesies while also washing your shirts that were not spared from the onslaught.

For babies, spitting up after feeding is very common. Due to the frequency of baby spit-up and the mess it causes, many parents find (or will discover) themselves searching for ways to remedy the situation.

Many parents will notice, one way or another, a pattern emerging in regards to their little one spitting up after feeding.

And it is not an encouraging pattern since many parents are aware of the benefits breastfed babies gain from their mothers’ breast milk.

The truth is that breastfed babies spit-up much more often than bottle-fed babies. Let’s explore some of the reasons below.

Formula vs. Breastmilk

The most important factor to consider when thinking about why breastfed babies spit-up more than formula-fed babies are the differences between breastmilk and formula.


  • The formula is manufactured in a factory allowing for uniformity and ingredient control.
  • It contains more protein, meaning formula-fed babies feed less often, minimizing baby spit-up chances.
  • Formula is heavier and has a thicker consistency than breastmilk, making it easier to keep down in the stomach.
  • It comes in different varieties (i.e., soy, lactose-free) that do not contain specific sensitivities or allergens like lactose or milk proteins (commonly found in cows milk and once digested transfers to breastmilk) that could be causing the spit-up.


  • Mom makes it. Breastmilk consists of around 200 different substances, which will vary depending on the mother’s diet and the baby’s needs.
  • The fat and protein content can change throughout the day and as your baby ages.
  • It is thinner in consistency, making it more likely to be carried up through your baby’s esophagus along with air when they burp.

Why do Babies Spit-Up?

More than half of healthy babies, especially babies between 1 and 2 months, will spit-up daily.

Some babies have even earned the title “happy spitters” because they spit up so often but are still gaining weight and do not exhibit any signs of stress or discomfort when they spit-up.

Developing Stronger Sphincter Muscles

Their sphincter muscles between their esophagus and stomach still need to develop and get stronger to prevent stomach contents from resurfacing.

Imagine burps and spit-up as a high-intensity training workout, which helps build their sphincter muscles.

Fast Let Down and Breast Milk Flow

If a mother’s breasts are overly full at the time of feeding, a strong let down reflex can cause a quick flow.

This may cause the milk to come out too fast, making the baby swallow air as they take big gulps and swallow quickly.

Burps Release Extra Air and Some Milk

They are teething or using a pacifier. Teething or using a pacifier may cause babies to swallow extra air as they drool more and swallow the excess saliva.

For adults, chewing gum can have a similar effect as it stimulates our salivary glands, and in turn, we swallow extra saliva.

Also, spitting up may happen if they burp after they feed to release the extra air. When babies burp, some milk is likely to come up as well.


Babies stomachs are tiny (the size of a hazelnut when born up to the size of a large hen’s egg at around ten weeks) and cannot hold much.

For comparison, an adult’s stomach is about the size of a grapefruit. If your little one has air in their stomach, this will lessen the space available for milk.

Food Sensitivities or Allergies

They are part of the small percentage of babies who have a food allergy to something passed through breast milk.

The most common is a dairy allergy, but other allergies to a variety of different foods have been reported as well.

Mothers who are breastfeeding should avoid eating spicy foods or foods with a high acid content, as this can increase the chances of your baby spitting up.

Reducing Spit-Up

Although spitting up after feeding is commonplace for babies, there are a few simple steps you can take to reduce spitting or at least ensure your little one is as comfortable as can be while their sphincter muscles develop and can keep the milk down.

Try Different Feeding Positions

Hold your baby in different positions (laid-back, cradle, crossover, football, etc.) while breastfeeding to find one that works the best.

The football position looks the coolest and has the best name. This laid-back position will help slow the flow if you have a strong let-down reflex by helping your child take the milk against gravity.

Also, ensure your child’s head is always above their feet when breastfeeding or if bottle-feeding.

Frequent Burps

Although it may seem counterintuitive as burps can cause babies to spit-up, babies should be burped between breasts and after every feed.

Burping should reduce the amount of air in your little one’s belly and coax the food down the esophagus into the stomach.

Keep Upright After Feeding

Remember they saying to wait 30 minutes after eating before going swimming? Similar to the advice we were given as kids, try to keep your baby upright for 30 minutes after they finish a meal.

Instead of engaging them in active play like bouncing or placing them on a play mat for tummy time, try reading a little story or playing calmly for 30 minutes.

Smaller, More Frequent Feedings

My feeding your little one a little more often, your can help avoid overwhelming their little stomach.

Also, try to avoid waiting until they are famished before feeding. This will help your little one eat at a nice pace rather than gulping air from feeding too quickly.

Relieve Pressure From Tummy

Release pressure by massaging your child’s belly. For example, lay your child flat on their back and apply gentle pressure in circular motions.

This can be done after feedings. Also, make sure their waistbands or diapers are not overly tight.

Pump To Slow The Flow

If you have an overabundant milk supply, make sure your little one latches properly and is not overwhelmed by the flow.

Try pumping excess milk or express a little before feeding to slow the flow.

Is Spit-Up a Problem?

Spit-up is very common among babies, and doesn’t need to cause any alarm.

Babies typically seem happy and content during a normal spit up after their meal.

Also, if your baby continues to gain weight at a normal rate, they are getting everything they need!

When to Call Your Pediatrician

  • You notice your child heaving. This is vomiting, and the heaving will cause it to project a lot more than spit-up. Vomit does happen, so if this only happens once or twice, it is not a cause for concern.
  • They may be fussier than usual and exhibit signs of pain or discomfort.
  • Your child vomits frequently or keeps vomiting after a 24 period.
  • Vomit has traces of blood or is green.
  • Symptoms of dehydration are present (i.e., dry diaper, no tears, no interest in feeding).
  • Your child is not gaining weight or loses weight.

Baby spit-up is very common for happy, healthy babies for various reasons!

Spit-up is most likely not a cause for concern, but if your child vomits, keep a close eye on them and call the pediatrician if necessary.