Why Does My Baby’s Poop Smell Like Fish? – Why & What to DO!

The use of unscented diapers can cause your baby’s poop to have a fishy, musty smelling poop.

For instance, my baby poop smells like fish when I use huggies (which are unscented) but when I use Luvs or Pampers, I don’t notice this smell because they are scented.

If that isn’t the case for you, then the rotavirus vaccine might be the cause. Some parents have reported this smell shortly after having their child take this vaccine.

Another possible reason for the fish odor in poop is poor absorption. This happens when the bowels move too quick and dump whatever it’s objecting to. The mucous comes from intestinal irritation (it creates additional mucous to try to protect itself).

So, check to see if you changed something in their diet. See if it gets better over the next few days. If not, or you see blood in the mucous stool, or actual watery diarrhea, it’s time to get your doctor involved.

Breastfed Baby Poop Suddenly Smells Bad

It’s either because you changed their diet or you used unscented diapers or they’re allergic to something.

If a strong odor persists over several days, it’s best to contact your child’s pediatrician and see if an allergy test is necessary.

Baby Poop Smells Like Rotten Eggs

If you’re feeding formula then it could be caused by malabsorption.

It is normal for babies who recently got rid of their meconium to have smelly eggs poop. It should take around a week and half for the egg smell to go away, though.

Fishy Smelling Poop Teething

Yes, this might happen and even cause loose nappies. When teething, your baby’s stool might smell fishy, runny or watery and sometimes mucusy. They may even smell like cheese and their urine smell very strongly of ammonia!

The child may be more prone to nappy rash (use a barrier cream on the nappy area to prevent this) as well. When the tooth busts through he or she will return back to normal. Although it can go on for a couple of weeks.

If the diarrhea continues for more than 7 days, contains blood, or is accompanied by vomiting do see your GP.

Baby Poop Smells Like Vomit

Teething, stomach flu, and gluten intolerance are 3 major causes of baby poo smelling like vomit.

For teething – there is pretty much nothing you can do other than wait it out.

For stomach flu – it might take 7-14 days for it to return to normal, even if the virus is passed earlier.

Gluten Intolerance – Cut out food items that contain gluten like wheat. This intolerance can also trigger rashes, weight gain issues, stomach aches, and sticky tar-like poop. The more it’s given to them the more it builds up in their system and the more problems they can have. It can take a while and a lot of gluten to see these symptoms.

My 4 Months old Baby Stool Smells Like Vomit

I bet it is teething. The acids in their mouths change from the drool which could cause acidic ouchy poops that have a funny smell. I’d give Tylenol if uncomfortable

Baby Poop Guide – My Babys Poop Smells Really Bad:

Newborn 0-3 months:

  • My baby is stooling less than usual. Should I be worried?

It is not a concern if your baby is otherwise doing well.

Most times, formula feeding babies poop at least once a day while breastfeeding babies may stool twice or more on a daily or only once per week. However, just like each baby is unique, pooping patterns wildly vary among infants of the same age.

Here are some signs you may need to see a doctor:

If your baby is feeding less or having fewer wet diapers

If the baby is spitting up much more than usual

If the baby suffers much more irritability than baseline

If the infant is within 2 weeks and it has been more than 3 days since he or she has had a bowel movement.

  • My baby’s poop turned green.

Green stool can be a normal variation of infant poop. Yes, as far as your baby is only having green stool and not showing any signs of distress, signs of illness or difficulty breathing there is nothing to worry about.

You should be alarmed if the green stool is accompanied by your baby feeding less, battling diarrhea, having a fever (rectal temperature of 100.4 or higher), or recent contact with fresh vomit.

Breastfeeding moms should be aware that getting more foremilk can sometimes make baby stools to turn green.

Green stool alone is not a sure sign of allergy or dietary intolerance.

ALSO SEE: Why Does My Floss Smell Like Poop?

  • How Can I Tell If My Infant Is Having Diarrhea

A lot of infant bowel movement is not formed and can appear to look like what adults would call “diarrhea” on a frequent basis.

The wisest thing to do here is to identify other signs of illness – fever (100.4 or higher rectal), poor feeding, or sudden increase in spitting up.

A recent change in the frequency of stool can also be a sure indication of diarrhea in a small infant. Stool that is 100% liquid or coming out of the diaper can mean diarrhea in a young infant.

  • What color stool should I be worried about?

Any Stool that bloody mucus, white stools, black stools, or red flecks are always concerning and you should contact your doctor to discuss your child’s symptoms.

Infancy (3 months- 1 year):

  • My baby’s poop smells weird/ bad/strange. Should I be concerned or ?

You should see a doctor if your baby’s poop smells like:

  • Rotten eggs or fish
  • Very sweet like maple syrup, or
  • The child is ill

If it smells normal or just a bit weird, then it can be monitored at home. However, if it smells like the 3 points we stated above, you need to see a doctor fast!

  • I Changed Something In My Baby’s Diet and Now Their Poop Changed. Is that normal?

A change in diet would most likely cause a change in the stool of your baby.

Little changes such as introducing formula to the diet of the infant or introducing solids would change the texture, frequency, and odor of their stool.

  • My Baby Started Eating Solids and Now They Are Straining To Pass A Bowel Movement Or Having Hard Stools. What can I do?

First, limit the starchy solids like rice cereal. You might also introduce a bit of 100% fruit juice into the diet to help soften things up.

Juice works best if fed at the end of the day, all at once. We recommend about 1 ounce for every month of life.

Also, make sure the little human is otherwise well hydrated and having regular wet diapers. If constipation is persistent, causing a lot of distress, or not improving after a few days of diet modification, you should always contact a doctor.

Toddlers (1 Year-3 Years):

  • My child is having hard stool, small pellet poops, or having discomfort or straining with passing a bowel movement, what can I do?

Ensure your child is having enough fluids to drink and having a frequent number of diapers.

Also, incorporate fiber in their diet by offering fruits, legumes, leafy greens, whole grains, beans, melons, beans, lentils, stone fruits, mangoes, peas, avocados, broccoli, and root vegetables.

Use processed foods with whole grains (e.g. whole wheat or fiber added pasta in place of white pasta).

Vegetable and fresh fruit based smoothies is a simple means of increasing fiber intake for a picky eater.

Crushed flax seed, chia seeds or oatmeal can give an extra fiber boost. You can offer up to 4 ounces of 100% fruit juice (non-diluted) every day and should limit cow’s milk intake to 24 ounces daily. If your child does not improve with home treatment, is vomiting, or has a decreased appetite drive you should always contact the office.

  • My Child Is Potty Trained, But Just Won’t Poop on The Potty, What Can I Do?

Positive reinforcement is the way to go when it comes down to potty training a child.

Families know their children best, so you need to decide what is the best motivator.

Common rewards are verbal praise, sticker charts, M&Ms, or anything you can get creative about!

  • My Child Seems to Be Withholding Bowel Movements, What Can I Do?

Talk to them and reward them for not withholding bowel movements.

If this fails, see a doctor.

  • My toddler has a Bowel Movement A Couple Times Daily, Or Their Poop Is Still Mushy, Is This Normal?

This sounds perfectly normal and is to be expected. Unless the stool is liquid, associated with acute illness, abdominal cramping, or appetite changes toddlers may have a bowel movement multiple time daily.

Softer stools or mushy poop can be a variant of normal, particularly if your toddler is eating a lot of fiber or loves fruit.

  • 2 Year Old Poop Smells Really Bad

You should see a doctor if your baby’s poop smells like:

  • Rotten eggs or fish
  • Very sweet like maple syrup, or
  • The child is ill

If it smells normal or just a bit weird, then it can be monitored at home. However, if it smells like the 3 points we stated above, you need to see a doctor fast!

  • 3 Year Old Poop Smells Really Bad

Go to the doctor and get them to send a sample of his poo off for testing. He may have a bug and need a course of anti b’s.

Sugar often causes problems. Lactose in dairy is sugar. Fructose is the sugar in fruit – sucrose (usual processed sugar) is in many products. All of these produce excess hydrogen when not processed properly.

  • Preschool Age and Beyond

Yes, ask your child how things are going from time to time so you’re ware of any discomfort, diarrhea, or constipation.


If your baby poo doesn’t poo too often then it should return back to normal within a few days. I wouldn’t worry about it.

Green poop can be normal on occasion. Consistent green poop can indicate an allergy or iron deficiency. It would be best to take a picture if it happens again and message your pediatrician.”

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