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Babies’ Poop Smells Like Vinegar: Why It Happens

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What does it mean when your babies’ poop smells like vinegar? Baby poop varies almost on a daily basis based on the little ones’ state of health and the food they’ve been eating. 

New moms know to monitor their baby’s poop because it can indicate whether or not the baby is getting enough to eat and drink. It also lets parents see how the baby’s digestive tracts are doing.

Let’s look into the possible reasons behind this foul problem.

Babies’ Poop Smells Like Vinegar: Why it Happens

The smell and look of baby poop usually reflect what your baby has had to eat and drink. That is why breastfed baby poop either smell sweet-ish or don’t smell at all.

Meanwhile, bottle-fed babies normally have more solid poop that stinks a bit.

When babies start eating solid food, their poop becomes more solid and really starts to smell. However, babies don’t typically produce poop that smells sour or acidic.

If your baby’s poop has a weird vinegar smell, it could indicate that he is not digesting his food well. It could also be the symptom of an illness, like a cold or a stomach bug, or a bad reaction to food or milk.

Some parents have even noticed that their babies begin making poop that smells like vinegar when they are teething.

Here are Some Possible Reasons Behind your Baby’s Sour Smelling Poop

Lactose intolerance — Baby poop that smells unusually sour can be the result of a sensitivity to the lactose in milk or other dairy products. Your baby can be sensitive to the milk you’re feeding him or, if he is breastfed, to dairy you consumed and passed to him through your breast milk. Lactose intolerance can also cause gas, diarrhea, and bloating, so watch out for these symptoms.

Malabsorption — When the nutrients from food are not absorbed well in your baby’s digestive tract, your baby’s poop can smell acidic. Malabsorption can be the result of a virus, a parasite, an infection, or certain disorders. It can also lead to weight loss and diarrhea.

Teething — There’s no scientific data to back this up, but some parents say that they’ve noticed vinegar smelling poop right before one of their little one’s teeth popped out.

Food sensitivity — Certain foods are hard on your baby’s digestive tract and are difficult to digest. One of the results is that your baby makes poop that smells acidic and is bulkier than usual. Common culprits include nuts, soy, dairy, and eggs.

Food allergies — If your baby has sour-smelling poop or poop that has some mucus or blood in it, he may have had an acute reaction to something he ate. That happens because some food can irritate the lining of the digestive tract. If you have a family history of food allergies, consult your doctor.

Rotavirus — This highly contagious virus can cause vomiting, loose black stools with a strong smell, and stools that have blood or pus.

Chron’s disease — Chron’s disease can result in poop that is watery, loose, explosive, and unusually sour. The stools may also have blood and mucus.

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Baby Poop Smells Bad: What to Look Out For

It’s normal for your baby’s poop to smell bad on occasion. It usually happens when a new food is introduced to his diet. But when there’s a sudden distinct change (e.g., foul smell, blood, mucus, diarrhea) in your baby’s poop, it may indicate a disorder or health issue that needs to be treated.

When this happens, you need to observe your baby closely for other signs of illness or discomfort. List down everything he ate and drank over the last few days, making sure to note any new foods you added to his meals.

If your baby has loose, smelly poop once or twice, it’s probably okay. But if it happens several times a day, call your doctor and get things checked out. Diarrhea can cause dehydration, so make sure your baby is getting enough fluids.


According to Seattle Children’s Hospital, if your baby exhibits any of these, call your doctor or bring him in for urgent care:

  • Fever
  • Irritability
  • Vomiting
  • Abdominal pain
  • Abdominal distention
  • Ten or more watery stools in 24 hours
  • Bloody stool
  • Dehydration is suspected (no pee in over 8 hours or pee is dark)

If your baby is younger than 3 months and has a fever or if your baby is less than one month old and has three or more watery stools, bring him to the ER right away.

Babies’ Poop Smells Like Vinegar: How to treat it

Don’t panic if your babies’ poop smells like vinegar. First, give it time to calm down (but not too long) and try making some diet changes, cutting out dairy products, changing his formula, or giving probiotics and see if it makes a difference.

If this doesn’t improve or your baby seems ill, see your doctor.

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