Why Does My Baby’s Poop Smell Like Vinegar? Is It Normal?

Only new moms can know the importance of a baby’s poop because it shows signs of your baby’s digestive tract health and other related issues. A baby’s poop largely depends on the state of health and the kind of food they are taking in. We know that your baby’s poop shouldn’t be smelly at all, but in case it is, it must be because your baby has started developing bacteria within his tummy. Hence, tracking your baby’s poop can help you detect any problem with your baby’s health. In case your baby’s poop has started to smell pungent or vinegary, then check what you or your baby is taking in if you are breastfeeding. Here are the possible reasons for your baby’s smelly poop and how you can determine if you need to change his diet or seek your pediatrician’s help.

A baby’s smell and shape of the poop reflects the diet they are taking in, which is why most breastfeeding babies either have a sweet-smelling poop or no smell at all. However, babies that are formula-fed normally have solid and a little stinky poop. According to a pediatrician, Adam Hart, Ph.D., professor of science communication at the University of Gloucestershire, UK, “If you breastfeed, your baby’s poop will probably look seedy and mustard-like, and if you bottle feed, expect something more greenish with the consistency of toothpaste.” Your baby is likely to have a little smelly and stinky poop upon starting solids, but it shouldn’t smell acidic or sour. An acidic or sour-smelling poop is an indication that your baby is not digesting his food well. This may happen because of an illness, stomach bug, or reaction to any food or milk. Some babies also tend to produce smelly poop during teething, so make sure that this is not the case with your baby first. Some of the common reasons for your baby’s acidic smelly poop can be lactose intolerance, malabsorption, teething, food sensitivity, food allergy, rotavirus, Crohn’s disease, and cystic fibrosis. Your baby may also show signs like fever, vomiting, abdominal pain, irritability, shortness of breath, inability to soothe, watery stools, abdominal distention, bloody stool, and dehydration, if he is experiencing any serious health issue, so watch out for the signs. Yellow, green, and brown are normal poop colors and do not indicate a serious problem. Red and black colored poops, however, are an indication of serious gastrointestinal bleeding. Sometimes your baby may have white poops, which is an indication of a disease or nutrient malabsorption. For an acidic smelling poop, give it some time and make changes to your or your baby’s diet and see if it solves the problem, but if the problem persists, then see your doctor immediately before your baby’s condition worsens.

Why do babies have smelly poops?

Why do babies have smelly poops?

Generally, the odor of a poop reflects how long the poop has been in the intestine; the longer the period, the smelly the poop would be. However, if your baby has a vinegar-smelling poop, then it must be an intolerance or allergy from the food he is, or you are taking in.

Usually, breastfed babies do not have smelly poops whereas, formula-fed babies may have a slightly odorous poop. Know that once your baby starts taking solids and various protein sources, you are likely to feel the smell of your baby’s poop.

If you believe that your baby’s bowel movements are exceptionally smelly, then consider talking to your pediatrician.

Possible reasons for your baby’s vinegar-smelling poop

Your baby could be having the following issues if his poop smells acidic:

Bad gut floral

Gut floral is a term used to represent the bacteria that exist inside a normal human’s intestine. Babies are born bacteria-free, and even if they do have bacteria, they are usually the “good ones” they need. But most of the babies get exposed to their mother’s bacteria during vaginal birth.

Research has shown that babies born via C-section may have those “good bacteria” disrupted, leading to a faster buildup of bad gut floral. This bad gut floral may cause your baby’s poop to smell like vinegar during his early days.

Lactose intolerance

Most baby stools that smell acidic or unusually sour result from sensitivity to lactose or other dairy products.

Your baby could be sensitive to the milk that you are giving him, or if he is breastfeeding, then the dairy you consume and pass on to him through your milk could be the leading cause of the smelly poop.

Lactose intolerance can also cause gas, diarrhea, and bloating in your baby so watch out for other symptoms as well.


In malabsorption, the baby’s digestive tract is unable to absorb the nutrients from the food well. This condition can also lead to an acidic smelling poop and may cause weight loss or diarrhea in your baby.

Malabsorption is caused by a virus, a parasite, an infection, or certain other disorders.


A baby teething could be the cause of smelly poops lately.

Though no scientific data approves teething as a cause of sour-smelling poop, many parents have noticed that their babies had smelly poop right before their teeth popped out.

Food sensitivity

Many foods that seem healthy can be hard on your baby’s digestive tract. If you have been giving your baby complex foods, he will most likely have smelly and bulkier poop than usual. Some of these foods are nuts, dairy, soy, and eggs.

Food allergies

Food allergies are prevalent among babies, so make sure that you focus on your baby’s bowel movements when introducing something new to their diet. In case your baby has a sour-smelling poop accompanied by either mucus or blood in it, it may indicate an acute reaction from something that he ate.

Food allergies happen when a particular food irritates the inner lining of the digestive tract. If you have a family history of food allergies, then consult your doctor before introducing your baby solids.


Rotavirus is highly contagious and can cause vomiting, loose black stools with a strong smell, and stools containing blood or pus. Consult your doctor immediately if you notice these symptoms in your baby.

Crohn’s disease

This is also known as chronic or long-term disease. This condition affects the digestive tract and causes inflammation and sores within.

Crohn’s causes malabsorption of nutrients and results in watery, loose, explosive, and unusually sour stools. Sometimes the stools may have blood or mucus in them.

Cystic Fibrosis

Cystic fibrosis is a severe genetic disease in which the lungs and digestive tract get clogged with mucus. Your baby will experience greasy stools and intestinal blockage along with pungent-smelling poop. CF also makes pooping painful and causes discomfort in your little child.

Symptoms to look out for if your baby has a smelly poop

An unhappy baby with his mom. Symptoms to look out for if your baby has a smelly poop.

Your baby’s poop is likely to smell at times, mostly when you introduce him to new food in your diet. But anything causing a distinct change like foul smell, blood, mucus, and diarrhea in your baby’s poop may indicate a health-related disorder.

To get to the root cause of your baby’s sour-smelling poop, watch out for the other signs of illness or discomfort. Please write down the list of foods or drinks you have been feeding him for the last few days. This will help you find out the food that may have caused the problem.

Having a smelly or loose poop once or twice is normal, but call your doctor for a checkup if it persists for several days. If your baby has diarrhea, then make sure to give him enough fluids to prevent dehydration.

If your baby exhibits any of the following signs of sickness, then call your pediatricians for a proper diagnose:

  • Fever
  • Irritability
  • Vomiting
  • Abdominal pain
  • Abdominal distention
  • Ten or more watery stools within a day
  • Bloody stool
  • Dehydration (no pee in 8 hours or a dark pee)

When to call a doctor

Call your pediatrician if you see the following changes in your baby’s poop:

  • Your baby’s poop is white (a symptom that your baby isn’t producing enough bile), black (a sign of blood digestion from the stomach or small intestine), or contains red streaks (a sign of blood from the colon or rectum).
  • Your baby cries while pooping.
  • Your baby has mucus in the poop, which indicates the sign of an infection or malabsorption.
  • Your baby’s stool changes significantly after taking in the new food. This is a sign of food sensitivity or food allergy.
  • Your baby has watery stools 5 or more times a day.


It is normal for a baby to have poop with an odor, so instead of panicking, give it some time, try to change the diet, cut out dairy products, change the formula, or give him probiotics and wait to see if it makes any difference. If all these changes fail to improve your baby’s smelly poop, then visit your doctor.

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Hajira is a certified editor, an experienced and thoughtful writer, and a mother of two. Her deliberate passion for writing convinced her to become a writer along with her mom duties. Driven by her passion for writing, she takes pride in providing the best possible. She aims to incite and provoke enthusiasm in her readers.

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