Baby Poop Smells Really Bad
Medically reviewed by Dr. Sarah Chen, MD, FAAP · Board-Certified Pediatrician
Content reviewed against published AAP, AAP, NIDDK guidelines
Last reviewed:
Digestive issues are common in infants and toddlers. If your baby is experiencing baby poop smells really bad, here is what you need to know.
The short answer
Baby poop smell changes significantly based on what they eat. Breastfed baby poop usually has a mild, slightly sweet smell, while formula-fed baby poop tends to smell stronger. Once your baby starts solid foods, poop will naturally start to smell more like adult stool. A sudden change to an unusually foul smell, especially with other symptoms, is worth mentioning to your doctor.
Key takeaways
- Baby poop smell changes significantly based on what they eat. Breastfed baby poop usually has a mild, slightly sweet smell, while formula-fed baby poop tends to smell stronger. Once your baby starts solid foods, poop will naturally start to smell more like adult stool. A sudden change to an unusually foul smell, especially with other symptoms, is worth mentioning to your doctor.
- Usually normal when: Your baby's poop smells stronger after switching from breast milk to formula or vice versa
- Call your doctor if: Extremely foul-smelling watery diarrhea with signs of dehydration, fever, or blood in stool
- Varies by age — see the age-by-age breakdown below
“The biggest concern with vomiting is dehydration. Young children can become dehydrated quickly, so it's important to replace fluids. Offer small amounts of an oral rehydration solution frequently.”
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What Parents Should Know
According to AAP, NIDDK guidelines, baby poop smell changes significantly based on what they eat. Breastfed baby poop usually has a mild, slightly sweet smell, while formula-fed baby poop tends to smell stronger. Once your baby starts solid foods, poop will naturally start to smell more like adult stool. A sudden change to an unusually foul smell, especially with other symptoms, is worth mentioning to your doctor. At 0-6 months (breastfed), breastfed baby poop typically has a mild, yeasty, or slightly sweet smell that most parents find inoffensive. A sudden shift to very foul-smelling stools in a breastfed baby can sometimes indicate a food sensitivity (often to dairy or soy in the mother's diet) or a mild infection. However, some variation in smell is completely normal. It is generally considered normal when your baby's poop smells stronger after switching from breast milk to formula or vice versa. However, you should contact your pediatrician promptly if extremely foul-smelling watery diarrhea with signs of dehydration, fever, or blood in stool.
Normal vs. Concerning
By Age
What to expect by age
0-6 months (breastfed)
Breastfed baby poop typically has a mild, yeasty, or slightly sweet smell that most parents find inoffensive. A sudden shift to very foul-smelling stools in a breastfed baby can sometimes indicate a food sensitivity (often to dairy or soy in the mother's diet) or a mild infection. However, some variation in smell is completely normal.
0-6 months (formula-fed)
Formula-fed babies generally produce poop that smells stronger than breastfed babies. This is normal and simply reflects how formula is digested differently from breast milk. Switching formula brands or types can change the smell. Hydrolyzed or amino acid-based formulas in particular can produce stronger-smelling stools.
6-12 months
Starting solid foods is the biggest factor in poop smell changes. Meat, eggs, and certain vegetables like broccoli and cauliflower can make stools smell noticeably stronger. This is completely normal and expected as your baby's gut adjusts to processing a wider variety of foods.
12-36 months
By this age, your toddler's poop will smell much more like adult stool. Very foul-smelling, greasy, or pale stools that float could rarely indicate malabsorption issues like celiac disease or fat malabsorption. If the smell is consistently extreme and accompanied by large, bulky stools, discuss this with your pediatrician.
What to Tell Your Pediatrician
- Describe when you first noticed baby poop smells really bad and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if your baby's stool has an extremely foul, rotten egg-like smell that is new and persistent.
- Mention if foul-smelling stools are accompanied by diarrhea, mucus, or increased gas.
- Bring a list of any questions or observations you want to discuss at the appointment.
What Should You Do?
When to take action
- Your baby's poop smells stronger after switching from breast milk to formula or vice versa
- Poop smells change after starting solid foods, especially meats and vegetables
- Your formula-fed baby has stronger-smelling stools than a breastfed baby you know
- The smell varies from day to day depending on what your baby ate
- Your baby recently took antibiotics and their stool smells different for a few days
- Your baby's stool has an extremely foul, rotten egg-like smell that is new and persistent
- Foul-smelling stools are accompanied by diarrhea, mucus, or increased gas
- Your baby produces consistently large, greasy, foul-smelling stools that float
- Extremely foul-smelling watery diarrhea with signs of dehydration, fever, or blood in stool
- Your baby has foul-smelling stools along with failure to gain weight or weight loss
What You Can Do at Home
- Keep track of when you notice baby poop smells really bad — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that your baby's poop smells stronger after switching from breast milk to formula or vice versa — this is generally within the range of normal.
- At 0-6 months (breastfed), focus on observation rather than intervention unless your pediatrician advises otherwise.
- Keep your baby upright for 20-30 minutes after feeding. Note any patterns between feeds and symptoms.
- While monitoring at home, seek immediate care if extremely foul-smelling watery diarrhea with signs of dehydration, fever, or blood in stool.
Related Resources
Poop Color & Texture Guide
What your baby's poop color and consistency mean, and when to worry.
Month-by-Month Development
Detailed monthly development guides from birth through 24 months.
When to Call the Doctor
General guide on when to call the pediatrician, visit urgent care, or go to the ER.
Frequently asked questions
Is baby poop smells really bad normal?
When should I call the doctor about baby poop smells really bad?
When is baby poop smells really bad normal?
What causes baby poop smells really bad?
What should I mention to my pediatrician about baby poop smells really bad?
Is baby poop smells really bad normal at 0-6 months (breastfed)?
Is baby poop smells really bad normal at 0-6 months (formula-fed)?
Should I go to the ER for baby poop smells really bad?
Does baby poop smells really bad go away on its own?
References
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss Baby Poop Smells Really Bad.
Things to mention
- Describe when you first noticed baby poop smells really bad and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if your baby's stool has an extremely foul, rotten egg-like smell that is new and persistent.
- Mention if foul-smelling stools are accompanied by diarrhea, mucus, or increased gas.
- Bring a list of any questions or observations you want to discuss at the appointment.
Observations to share
- Your baby's stool has an extremely foul, rotten egg-like smell that is new and persistent
- Foul-smelling stools are accompanied by diarrhea, mucus, or increased gas
- Your baby produces consistently large, greasy, foul-smelling stools that float
Urgent signs to report immediately
- Extremely foul-smelling watery diarrhea with signs of dehydration, fever, or blood in stool
- Your baby has foul-smelling stools along with failure to gain weight or weight loss
My notes
From ismybabyalright.com — free, evidence-based baby health guides
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members
Related Resources
Bottom line
Most cases of baby poop smells really bad are normal. Talk to your pediatrician if extremely foul-smelling watery diarrhea with signs of dehydration, fever, or blood in stool.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
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