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Top Reasons For Smelly Bowel Movements In Babies

reasons for smelly diaper
The girl is just cute – not the one in the article 🙂

Mom’s Question: My daughter is 7.5 months old, she is on Similac formula, nestle rice cereal and Heinz baby food, and her stool is green, mucousy like and it smells really strong. I have never known a baby (which I have been around a lot of) to have this strong smell to their stool.

I was just wondering if this is something to cause concern or if it is a side effect of either her food formula or teething.

Vanessa (B.C. Canada)

Baby Helpline:

Reasons For Smelly Baby Stools

The smell of babies’ stools can vary a lot just like with adults. What they eat as well as their health will make the smell more or less strong.

Breastfed babies often do not have strong smelling stools. A study from 2001 found that the stools of formula-fed babies contained a lot more odor-causing sulfur gases than breast milk poop. When a baby starts eating solid foods, the feces will change again; often to the worse when it comes to smell.

In addition to these normal variations, the baby’s stools can also be affected by a stomach bug, a cold, food intolerance or even that the baby is teething.

Despite a complete lack of research studies on this, many parents agree that their babies’ stools suddenly smelled like vinegar just before one of their baby’s teeth popped.

A sudden shift in the smell, and especially if combined with a change in consistency to the worse (diarrhea, gas, or mucus for example) often indicates that something is wrong. In addition to watching your baby for other signs of illness or teething, you can also then think back on any new foods recently introduced, and take them away to see if it helps.

Green poop, a strong smell and gas, can be due to lactose overload.

A strong smell and very frequent pooping can indicate Rota virus, regardless of poop color.

Since there are so many reasons why a baby’s stools may start to smell, the best you can do as a parent is to look for other signs of teething as well as illness and also think back on any introduction of new foods or formula. If your baby seems to be ill, consult a doctor of course.

P.S. Here are two excellent reference books for baby health issues and injuries:

More Baby Poop Issues

Find comments to this question below.


Feb 02, 2013

possibly teething
by: Anonymous

More than likely it the teething My daughter experienced the same type of smelly diapers. It almost smells acidic. It will eventually go away just bare with it when those pearly whites pop threw it will be worth it believe it or not.

Feb 02, 2013

thats the smell

by: Anonymous

yes thats what it smells like acidic kinda i cant wait for the those teeth to come in and the smell. Thank You

Feb 05, 2013


by: Anonymous

It could also be an allergic reaction. We had a similar problem with my 10 month old after I gave her wheat cereal! Try eliminating it for a few days and bring it back to experiment. They smell more with solids too!

Mar 07, 2013

My baby too

by: Anonymous

I have been going through the exact same thing with my 9 month old son, for almost 2 weeks. The only new foods I’ve given him are Yogurt Melts and Cheerios. He has eaten my yogurt and baby cereal before with no problem, so I thought it shouldn’t be the new foods. He IS teething and they are hurting him…I hope it is the teething. How interesting.

Mar 12, 2013



You are giving a 9 month baby Cheerios. Why? They contain a lot of sugar.

If the stool is green, take the baby to the doctor. Rotavirus is associated with green stool and a strong smell.

Jun 19, 2013

smelly movements

by: Anonymous

What’s the big deal with cheerios?? I have been giving them to my little girl since she was 6 months and her pediatrician suggested it!

Thanks for the tip on rotavirus, though, I’ll have to check that up!

Dec 08, 2013

Smelly poop

by: Anonymous

My 9 month old son has really smelly poop and im wondering if i should be worried. His poop is the normal every day color from the baby food i give him, yes he is teething and yes he is on similac senivitive formula. So what should i do

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