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Why Does My Baby’s Breath Smell Sour And How to Get Rid Of It?

Babies aren’t able to tell us when something is wrong. Smaller children that can talk often don’t have the vocabulary necessary to say that they have something stuck in their nose or that their stomach hurts.

Instead, they cry. If not, you’ll notice other symptoms. If you notice that your baby’s breath smells sour, this is a signal that something else is going on.

Your baby’s breath can tell you if they have acid reflex, cavities, are dehydrated, and several other things. It’s important to learn what this can mean so you can make sure that your little one is always feeling their best. 

Why Do Babies Sometimes Have Sour Smelling Breath?

When you first notice that his baby breath smells sour, it can cause a slight panic. This isn’t as common as the internet insinuates, but it’s more than likely nothing serious.

First, consider the minor things that could be the culprit. Then, consider more serious options and contact your pediatrician. 

Oral Hygiene

Our mouths are packed with bacteria. If your little one has teeth, it’s possible that the bacteria is in between their adorable teeth. Make sure that you’re brushing their teeth properly.

They should be brushed at least twice daily. Toddlers may be able to help brush their teeth, but they aren’t old enough to brush their teeth on their own.

You can use a finger brush and fluoride toothpaste to make sure that you’re brushing your baby’s teeth thoroughly. 


This means that the sinuses are inflamed. Chronic sinusitis can present itself in infants, and parents will notice several other symptoms of this condition.

Common symptoms of sinusitis in infants are: 

  • Loss of smell
  • Fever
  • Pain where the sinuses are located
  • Congestion
  • Postnasal drip
  • Headache (it might be difficult to tell if a baby has a headache. If they cry at noises or flinch as though noises seem louder than usual, this is a sign that they have a headache.)

Common methods, such as saline drops and using a nasal syringe, can help clear congestion in infants. If an infant has a bacterial sinus infection, your pediatrician can prescribe antibiotics. This will clear up the sinus infection as it kills the bacteria. 

Acid Reflux

Acid reflux, which is commonly referred to as gastroesophageal reflux or GERD, is when stomach acids are regurgitated up into the esophagus.

This results in stomach pain, heartburn, and can lead to sour breath in infants. Common symptoms of acid reflux include: 

  • Vomiting
  • Coughing
  • Wheezing
  • Choking or gagging when feeding
  • Refusing to eat
  • Gas
  • Fussiness
  • Heartburn
  • Crying following eating

These are the most common symptoms, but babies may have other symptoms, suck as being colicky.

baby with mother and doctor

Treatment For Acid Reflux

Consulting with your pediatrician can verify that baby breath smells sour due to acid reflux. However, there aren’t a lot of medications for infants, especially for acid reflux.

Remember that most children outgrow this by the time they hit a year old. In the meantime, these common changes can usually help your little one feel better: 

  • Elevate their head. This could be in their crib or bassinet. Being slightly elevated can help reduce the symptoms of reflux because laying down makes it harder for the body to digest foods. 
  • Make sure to hold your little one in an upright position for at least 30 minutes after eating
  • Increase solid food intake, as long as it’s okay with your pediatrician
  • Thicken formula with cereal if your pediatrician says it’s okay
  • Feed smaller amounts at a time as overfeeding can worsen symptoms of acid reflux

Before giving your little one cereal or solid foods, it’s important to make sure that this is okay with your pediatrician. If your baby is too young for cereal or solid foods, they’ll more than likely recommend other methods to see if they work first.

Remember, it might take a few days to see a difference in your little one. Try one method at a time to figure out what works, and what doesn’t. 

If you don’t notice any of these symptoms yet but do notice that baby breath smells sour, contact your pediatrician. They can help determine the underlying cause of sour-smelling breath. 

Does Your Baby Have Breath That Smells Like Fart Or Poop?

When you’re dealing with baby breath that smells closer to feces than anything else, it can be alarming at first. Fortunately, there are several perfectly normal things that can cause this nasty smell.

Most of them are easily treatable. The same things that will make you notice baby breath smells sour can also lead to baby breath that smells like poop. These are: 

  • Poor oral hygiene
  • Sinus infection
  • Reflux

These are the ones that both smells have in common, so if you notice this one day and a sour smell the next, one of these three could be it. However, there are other reasons that your little one has breath that smells like poop.


Saliva helps control the bacteria in your mouth. When a person is dehydrated, they have less saliva, which leads to them not being able to control the bacteria as well as they would be able to if they were hydrated.

baby drinking

This can result in an overgrowth of bacteria, leading to a horrible smell. People that are sick, such as those that are vomiting or have diarrhea, will quickly become dehydrated.

To re-hydrate children: 

  • Drink small amounts of fluids at a time instead of larger amounts
  • Eat small amounts of fruit, such as watermelon, that are packed with water

Severe cases of dehydration might need to be treated by an emergency room, instead. They can hydrate people quickly with IV fluids.

If you’re concerned that your little one is severely dehydrated, taking them to the emergency room or contacting their pediatrician is a great idea. It’s always better to be safe instead of sorry. 

Bowel Obstruction

A bowel obstruction happens when there’s a blockage in the intestines. This can prevent a person from being able to pass bowel movements properly.

As time goes on, things will start to get severely backed up towards the other direction. Common causes of this are being constipated, eating foods that can’t pass through your digestive tract, and other medical conditions that cause a blockage.

This can cause a breath that smells like poop. Some people that are severely backed up might throw up feces, too. This requires medical treatment.

Other symptoms of a bowel obstruction include: 

  • Not passing bowel movements like previously did
  • Abdominal pain
  • Vomiting
  • Nausea
  • Not being able to pass gas
  • Bloating

Remember, a bowel obstruction can be very serious. It’s important to call a doctor or take your child to the emergency room if they are experiencing these symptoms, or if you are concerned. 

What About Breath That Smells Like Vomit Or Spoiled Milk?

Your baby’s breath can tell you a lot about how they are doing. If it smells like vomit or spoiled milk, it’s not necessarily a sign that something is wrong.

These are some of the most common reasons you’ll notice that your little one’s breath smells bad.

baby milk in a bottle

High Protein, Low Carb

Most baby formula has everything that your little one needs. If your baby is strictly bottle-fed, this more than likely is not the problem. 

Babies that are breastfed wind up with the same things in their diet that their mom has. If you’ve started dieting or cutting back on certain foods while breastfeeding, that could be to blame.

A large amount of protein and a low amount of carbs will specifically cause that problem. 

Older babies that are on solid food are more prone to have a low carb diet. This is because some babies don’t care for the texture of bread or pasta, which is where they get a lot of carbs from.

If this is the case, try these other foods that have carbs in them to make sure that your little one is meeting their daily requirement: 

  • Oatmeal
  • Cereal
  • Crackers
  • Potatoes
  • Milk
  • Juice
  • Fruits

Try changing your kid’s diet to see if that resolves the issue if they are old enough for solid foods. Usually, bad breath can be due to a person’s diet or health. 

High Lipase In Breast Milk

Before rushing to the pediatrician, take a good whiff of your breast milk. Breast milk has an enzyme called lipase in it. Some people have a higher amount of lipase than other people do.

This can result in the breast milk smelling sour. It’s common for breast milk to smell like this after it has been frozen and thawed because the enzymes can separate. Most of the time, babies do not mind, but it can result in their breath smelling sour.

breast milk

Lactose Intolerance

Lactose intolerance is very common in babies. Infants on formula are exposed to lactose as are older children. Other signs of lactose intolerance include:

  • Stomach cramps
  • Bloating
  • Gas
  • Diarrhea
  • Upset stomach
  • Indigestion
  • Colic

If this is due to lactose intolerance, eliminating lactose from the diet will solve the above problems. If the only symptom present is that the breath smells like sour milk, it’s unlikely that it’s due to lactose intolerance. 

Final Thoughts

Other common problems listed above, such as bad oral hygiene, sinusitis, and acid reflux can all result in the breath smelling like sour milk. 

When various smells can all be the same thing, it can be difficult to determine the underlying cause. First, look for other symptoms that are occurring at the same time. Examine your child’s diet as well. If your baby is breastfed, take your own diet into consideration. If the issue persists, symptoms are concerning, or you feel concerned, consult your pediatrician. If your baby has symptoms of bowel obstruction, it’s important to seek help immediately. 

Medical Disclaimer. All content and media on the MomInformed Website is created and published online for informational purposes only. It is not intended to be a substitute for professional medical advice and should not be relied on as health or personal advice.