Baby Poop Smells Like Vinegar: What It Means, When To Worry

| Reviewed By Amanda Lundberg, BSN, RN

Expecting parents and new parents worry a lot about their new baby. Is the baby eating enough, having enough wet or dirty diapers, warm enough?

The list could go on, but one thing expecting parents might not realize they will be paying such close attention to is baby poop!

When a baby is born, the hospital will have you write down when the baby has a wet or dirty diaper, and this is a practice many new parents continue once they are back home.

You just do not know how much attention you will be paying to poop until you have had a baby. 

Why does my baby’s poop smell like vinegar? A baby’s poop can smell like vinegar for a number of reasons, most of which have to do with digestive issues, such as nutrient malabsorption, a gut imbalance, a change in diet, and food sensitivities, but teething, medications, illness, and even allergies can cause a vinegar smell as well. 

If you go to change a baby’s dirty diaper and get a smell of vinegar, as a new parent, it can be scary.

There are a few reasons this can happen, and most of them are not so scary, but there are a few more concerning issues that might be going on. 

Baby Poop Smells Like Vinegar – 9 Possible Causes

One way to keep an eye on the health of your baby is to monitor how their poop looks and smells. Breastfed babies will have different poop than formula-fed babies.

Certain illnesses can cause a change in a baby’s poop. Knowing what to look for can help you notice signs that your baby might need to see a doctor. 

1. Nutrient Malabsorption

Malabsorption is the difficulty of absorbing nutrients, sugars, proteins, or vitamins. Since a baby has an underdeveloped digestive system, they can be at risk of not being able to digest essential nutrition.

If a baby is having trouble with malabsorption, this can cause their poop to have a vinegar smell to it. Some viruses, parasites, or even genetics can cause a baby to have malabsorption. 

2. Gut Microflora Imbalance

Microflora is known to be a good bacteria in the gut. When a baby is delivered vaginally, they receive the benefits of good bacteria that are needed to help their digestive system.

However, if a baby is born by c-section, they do not receive the same benefits. This could leave the baby’s microflora balance off, resulting in digestive problems. 

3. Medications

If a baby is taking antibiotics, this can cause an imbalance of microflora (good bacteria) in the gut.

Once this balance is off, there will be an overgrowth of bad bacteria resulting in a vinegar smell and mucousy poops from the baby.

Also, medications that have diarrhea as a side effect can disrupt the baby’s digestive system, throwing off their microflora (good bacteria) balance.

4. Allergy

Allergies to certain things could cause a baby to have sour-smelling poops.

If the baby is allergic to something they are consuming, it will cause a rise in the acidity levels in their bowels. The rise in acidity levels could cause the poop to have a vinegar smell to it. 

5. Crohn’s Disease

Crohn’s disease is a disease that causes chronic inflammation in the gastrointestinal system. This disease also prevents the child from being able to absorb nutrients.

Between these two components, the baby will suffer from malabsorption and microflora imbalances, both of which are known to cause the poop to smell like vinegar.

6. Food Sensitivity

The most common food intolerance is dairy or lactose. For a formula-fed baby, they sometimes need to be placed on a formula brand that has more broken-down lactose so it is easier for them to digest.

If a mother is breastfeeding and consuming dairy, it is then passed on to the baby through her milk. The baby could have other common food intolerances including soy, corn, and gluten.

Food intolerances in a baby can appear similar to an allergy, raising the acidity in the digestive tract and leading to sour-smelling bowel movements. 

7. Sudden Diet Change

A sudden diet change can lead to a change in the baby’s stools. If a formula-fed baby changes formulas and their digestive tract is not used to it, there could be some problems with the baby’s poops.

If a breastfeeding mother suddenly changes her diet, the nutrients and ingredients in her milk then change also, causing a difference in what the baby’s digestive tract is used to. This could lead to an upset stomach, mucus in the stool, or even the smell of vinegar in the poop.  

8. Rotavirus or Other Illness

Rotavirus is a virus that causes excessive diarrhea, vomiting, fever, and dehydration. During the time the baby has this virus or any other illness that causes similar symptoms, they can have vinegar sour-smelling poops.

Cystic fibrosis is an inherited disease that can cause blockages in the digestive system.

A blockage in the digestive tract can cause the juices and mucus to become sticky and thicker. These thicker juices can cause problems with the enzymes in the digestive tract, resulting in problems absorbing nutrients.

9. Teething

Parents have reported that some teething babies have occasional vinegar-smelling poop. It is unclear why the smell of their poop changes during teething, but it could be because of the excessive drool and increased diarrhea. 

A father with a shocked, disgusted look on his face as he peels the diaper off his baby.

Normal Breastfed Baby Poop

Normal poop in a breastfed baby is usually yellow and seedy. A healthy breastfed baby’s poop might even have a sweet smell to it.

As the baby gets older, it is normal for a healthy breastfed baby to not have a bowel movement every day. Since breastfeeding is tailored just for babies’ needs, they are able to absorb most of the nutrients, leading to fewer bowel movements. 

Normal Poop for Formula-Fed Babies

Babies who are fed formula will have bigger, more solid poops than a breastfed baby. Their poop will be yellow or brown in color and be the consistency of peanut butter. 

When To Be Concerned About Your Baby’s Poop

A parent should be concerned if the baby has excessive diarrhea or if the baby’s poop contains a lot of mucus or any blood. If a baby’s poop has a vinegar smell to it, it might be worth talking to the doctor about. 

Related Questions:

Why Is My Baby Pooping So Much?

Increased bowel movements in a baby can mean many things. Breastfed babies in the newborn stage nurse a lot, which causes them to have more frequent poops, sometimes even every diaper change.

A change in a baby’s diet can cause more bowel movements. Also, if the baby is sick or teething, they may have more poops. 

How Often Should a 1-Month-Old Poop?

A healthy 1-month-old baby can have up to 10 dirty diapers a day. As long as the baby is not having excessive diarrhea, there is no mucus or blood in their poop, and it looks fairly normal, there is nothing to worry about. 

Final Thoughts

In babies and even adults, the way the stool smells or looks is an indication of a person’s health. Knowing what is normal or not is a good way to help monitor your baby’s health.

Your baby’s poop will change with age and their diet. If you are concerned about your baby’s bowel movements, it’s always important to speak to their doctor.