Babies Poop Smell like Vinegar: Reasons and Solutions

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Babies’ poop tells us about the health of the baby. But when babies’ poop smell like vinegar, it makes you wonder what is wrong with the baby. Read on to learn about reasons and solutions.

Newborn’s poop varies on an everyday basis for the first few months. And it is very important to monitor your baby’s poop and pee for the first few weeks, which keeps you in check about whether your baby is getting enough to eat and drink. 

Usually, breastfeeding babies’ poop does not smell or have a sweet smell. But if your baby’s poop smells like vinegar, you may need to find out why. 

If your baby’s poop is loose and smells sour once or twice, there is nothing to worry about. But if babies’ poop smells like vinegar often, you may need to contact your pediatrician. 

women holding diaper and squishing nose with hands

When babies’ poop smell like vinegar, it usually indicates that certain nutrient from food did not absorb, the baby is lactose intolerant, or the baby has food sensitivity or allergies. Sometimes a viral infection can also cause poop to smell like vinegar. Sour-smelling poop can also indicate a condition like Chron’s disease, kidney disease, or Cystic fibrosis. 

Let’s examine why your breastfed or formula-fed babies’ poop smell like vinegar.

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Breastfed Babies’ Poop 

Healthy breastfed babies’ poop is usually mustard yellow, brown, or green in color. It is also a little watery (loose), pasty or seedy in texture. 

yellow mustard poop in a diaper_ babies poop smell like vinegar

Breastfed babies poop often and do not smell or have a mild sweet smell, which is due to the fact that breastmilk is easier to digest and is mostly absorbed in the gut. So, their poop is the leftover of the digested breastmilk. 

Because breastmilk gets digested faster (that’s why they poop as they feed), it does not stay in the gut for a longer time, hence does not accumulate bacteria which is usually responsible for smelly poop. 

But when breastfed babies’ poop smells, something is wrong with their diet that you will need to investigate. 

Formula-fed babies’ Poop

Formula-fed babies’ poop is a shade of yellow/brown with a pasty consistency. It is often of a peanut butter consistency and a little more solid than breastfed babies’ poop. Their poop also has a stronger smell.

This is because formula takes longer to process and digest, which causes formula particles to sit longer in the gut with bacteria. 

When babies start solids, their poop will have a stronger smell. And depending on the baby’s diet, their poop will smell different.

For example, in a baby’s diet, vegetables, fruits, beans, onions, and garlic contribute to smelly poop. 

Why does my Babies’ Poop Smell like Vinegar? 

Babies’ poop is typically odorless if breastfed or has a mild smell if formula fed. But if their poop has a sour smell or poop smells like vinegar, then you need to investigate why that is. 

If your baby’s poop smells like vinegar or sour for a day or two, you usually do not need to worry about it. But if the smell persists, there could be the following reasons. 

Lactose Intolerance

Lactose Intolerance can cause your baby’s poop to smell sour or vinegary. Lactose intolerance is caused by the unavailability of the enzyme lactase, which breaks down lactose into simple sugar, so it gets absorbed in the gut. 

Lactose Intolerance in babies can cause babies’ poop to smell sour or acidic. In addition, lactose intolerance babies can experience bloating, abdominal pain, gas, and diarrhea. 

Food Allergies 

Once the baby reaches the age of starting solid, you might be excited to introduce new food to your baby.

But you need to be careful about introducing fresh food to your baby because usually, at this time, you will discover any food allergies or sensitivity that your baby might develop. 

When you introduce solids to your baby, their poop color and consistency will change. Your baby’s poop will also have a stronger smell. 

If your babies’ poop has a foul odor or sour odor, there is something in their diet that they are not digesting.

That’s why knowing how to start solids in your baby is important. Check out this guide on when and which food to give to your baby and how long you should wait before introducing new food to your baby. 


When nutrients from certain food are not absorbed in your baby’s digestive system, it causes babies’ poop to smell sour, acidic, or vinegary. 


baby in a blue hat chewing hands

Teething can also cause poop to smell like vinegar or acidic. However, there is no scientific evidence to back this up.

Sometimes (but not always), when baby is teething, they have diarrhea. Since diarrhea is moist and acidic, it may cause poop to smell acidic or like vinegar. 

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Viral or bacterial Infection of the gut can produce foul-smelling poop. For example, E.coli or salmonella Infection in a baby can cause poop to have a distinct odor. 

But when they have a Rotavirus infection, their poop smells like vinegar. Rotavirus is very contagious and is a leading cause of severe infectious diarrhea in children. 

This virus is most often spread through the fecal-oral route, so unhygienic practice while handling a baby can cause the spread of rotavirus.

In addition, rotavirus can be found on surfaces like door knobs, changing tables, toys, and other hard objects for a long time.   

Consuming contaminated food and water can also cause rotavirus infection. If not treated, rotavirus infection can cause severe dehydration. 

Cystic Fibrosis

Cystic fibrosis is hereditary and can cause your baby’s poop to smell like vinegar or acidic.

This condition affects how salt and water move in and out of cells in your body, thereby affecting glands that secret mucus, tears, sweat, saliva, and digestive juice. 

In babies with cystic fibrosis, the secretion is abnormally thick and sticky and clogs the lungs and digestive system.

Cystic fibrosis is usually screened at birth, so if your baby has cystic fibrosis, you will know soon after birth. 

What can you do if your baby’s poop smell like vinegar?

Knowing the causes of vinegar-smelling poop, it will be easy for you to remedy it immediately before it becomes a bigger issue. 

If your baby’s poop smells like vinegar for a day or two and is not associated with other symptoms, you do not need to worry about it. But if the problem is consistent and you see other signs like 

  • fever
  • abdominal pain
  • Watery stool multiple times a day
  • Excessive crying
  • Shortness of breath
  • Blood in stool

Then you need to consult your pediatrician soon. 

If your baby is lactose intolerant, you can try lactose-free formula milk or low-lactose formula once you confirm with your pediatrician. And then monitor your baby’s poop; if it still smells like vinegar, talk to your doctor. 

If your baby has rotavirus infection, they will have diarrhea and vomiting. Rotavirus infection is easily treated. Talk to your pediatrician.

The most important thing to consider when your baby has a rotavirus infection is to hydrate them frequently. 

For a severe condition like cystic fibrosis, you will know soon after the birth of your baby as they are screened for cystic fibrosis shortly after birth. 


When should I worry about the baby poop smell?

If your baby’s poop has a foul smell or smells like vinegar, it might mean that they are allergic to something they have eaten or their digestive system can not digest certain nutrients from the food they have eaten. 

If this foul or vinegar smell persists for several days and is associated with other symptoms like fever, diarrhea, abdominal pain, excessive crying, or gas. In that case, you need to contact the pediatrician. 

Why does my baby’s poop smell like vinegar and Green?

Baby’s first poop is green because of meconium but then turns mustard yellow (if breastfed) and tan-brown (if formula fed). 

But if your baby’s poop smells like vinegar and is green in color, it indicates that your baby may have a food intolerance to something in breast milk or formula. If your baby is food intolerant, it may show other symptoms like irritability after feeding. 

Why does my 1-year-old baby’s poop smell like vinegar?

If your 1-year-old baby’s poop smells like vinegar, you might want to look for rotavirus infection. Because if they come in contact with other sick kids, they can get infected with rotavirus, a highly contagious virus. Look out for other symptoms like diarrhea, vomiting, and abdominal discomfort. 

Another possibility is the introduction of new food. For example, if your baby is intolerant to certain nutrients from their food, it may cause their poop to smell like vinegar. 

Observe their poop for a few days; if the vinegar smell in poop persists, contact your pediatrician. 

How to tell if the baby is lactose intolerant? 

Lactose intolerance is caused by a lack of the enzyme lactase, which breaks down lactose into simple sugar, so it gets absorbed in the gut. 

Symptoms of lactose-intolerant babies are 

  • Diarrhea
  • bloating
  • gas
  • stomach pain or cramping

Since babies can not communicate, you may want to look for the following signs that they exhibit 30 minutes or 2 hours after breastfeeding or formula feeding, or solid food containing dairy. 

  • Arching their back
  • clenching their fists
  • crying while passing gas 
  • Stomach hard to touch

If you see any of these symptoms, talk to your pediatrician. 


Babies’ poop constantly changes in color and consistency during the first few months of their life. Then, depending on whether they are breastfed or formula-fed, their poop color and odor change. 

Breastfed baby poop is almost odorless, while formula-fed baby poop has a distinct odor. But it is worrisome when your babies’ poop smell like vinegar or their gas smell like rotten eggs. 

If your baby’s poop smell like vinegar, go through the possible causes given above. Once you know the reason, you can contact your pediatrician if you can not handle it at home. 

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