The Sour Smell Of Newborn Poop: Why It Happens

Newborns' poop can smell sour for a variety of reasons, and it's important to know when to be concerned and when not to worry. The colour and smell of a baby's poop can indicate their health and growth status, and while some smells are normal, others can indicate an underlying issue.

The first poop a baby passes is called meconium, which is a mixture of amniotic fluid, bile, mucus, lanugo, skin cells, and more. Meconium is thick, dark in colour, and very sticky. After the first 24 to 48 hours, the meconium will transition into a thinner, looser greenish-brown or greenish-yellow transitional stool.

Breastfed babies' poop usually has a milder odour and tends to be yellow in colour, with a seedy texture. Formula-fed babies, on the other hand, tend to have firmer and more odorous poop, ranging from shades of tan to brown.

If your baby's poop smells sour, it could be due to several reasons:

- Lactose intolerance: Babies may develop sour-smelling poop if they are sensitive to lactose in milk or dairy products. Lactose intolerance can also cause gas, diarrhoea, and bloating.

- Malabsorption: When nutrients from food are not properly absorbed in the baby's digestive tract, their poop can smell acidic. Malabsorption can be caused by viruses, parasites, infections, or certain disorders, and it can lead to weight loss and diarrhoea.

- Teething: Some parents have noticed a vinegar-like smell in their babies' poop right before a tooth erupts, although there is no scientific data to support this.

- Food sensitivity: Certain foods, such as nuts, soy, dairy, and eggs, can be hard for babies to digest, leading to acidic and bulkier poop.

- Food allergies: Sour-smelling poop with mucus or blood in it could indicate an acute reaction to something the baby ate, as certain foods can irritate the digestive tract lining.

- Rotavirus: This highly contagious virus can cause vomiting, loose black stools with a strong smell, and stools containing blood or pus.

- Crohn's disease: This inflammatory bowel disease can result in watery, loose, and explosive stools with an unusual sourness. The stools may also contain blood and mucus.

- Cystic fibrosis: This hereditary disorder affects mucus production and can lead to thick and sticky mucus and digestive juices, making it difficult for babies to digest food.

While an occasional sour-smelling poop is usually not a cause for concern, if it persists or is accompanied by other symptoms, it's important to consult a doctor. Diarrhoea can lead to dehydration, so ensure your baby stays hydrated, and look out for signs such as dry lips, sunken eyes, or sunken fontanels (soft spots on the baby's head).

Food allergies

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

Signs of Food Allergies

• Abdominal distension
• Ten or more watery stools in 24 hours
• Dehydration (no pee in over 8 hours or dark-coloured pee)
• Fever (if your baby is younger than 3 months)
• Three or more watery stools (if your baby is less than one month old)

What to Do if You Suspect Food Allergies

If your baby is displaying any of the above symptoms, call your doctor or bring them in for urgent care. Diarrhoea can cause dehydration, so make sure your baby is getting enough fluids.

Lactose intolerance

Symptoms of Lactose Intolerance in Newborns

• Watery, loose stools
• Gas
• Diarrhea
• Bloating
• Abdominal pain and cramping
• Nausea
• Malnutrition or failure to thrive

Causes of Lactose Intolerance

There are several types of lactose intolerance that can affect newborns:

• Congenital lactose intolerance: This condition is passed down genetically and is present from birth. Babies with congenital lactose intolerance will show signs right away, with symptoms such as watery diarrhea developing within the first few days of life.
• Developmental lactose intolerance: This type of intolerance is also present at birth and affects babies who are born prematurely (before 34 weeks' gestation). Premature babies may have lower levels of lactase because this enzyme is typically produced late in the third trimester.
• Secondary lactose intolerance: This can affect babies, children, and adults. It occurs when the small intestine reduces its lactase production in response to illness or injury. In babies, this may develop after a bout of severe diarrhea, malnutrition, or other illnesses.

Diagnosis and Treatment

If you suspect your newborn has lactose intolerance, it is important to speak with your doctor to receive a correct diagnosis. The rare baby with congenital lactose intolerance should be given a lactose-free formula to prevent weight loss and dehydration, which can be life-threatening if not treated promptly.

For older babies who are eating solid foods, try focusing on calcium-rich alternatives to dairy to ensure they get enough calcium in their diet. These include foods like calcium-fortified soy or other milk substitutes and calcium-fortified breads and juices. You may also want to discuss supplements with your pediatrician to support your baby's vitamin D levels.

Malabsorption

The digestive system of young children is still very immature, and they are unable to absorb nutrients completely. This is a normal condition, and parents can handle it at home without being too worried. However, if the baby's stool has a sour smell and is accompanied by other symptoms, such as diarrhoea, foamy stools, fever, vomiting, abdominal pain, paleness, fatigue, and irritability, it is important to take the baby to a medical facility for an accurate examination and diagnosis.

Teething

Signs Your Baby Is Teething

• Biting and sucking: Babies may bite and suck more when they're teething as a way to soothe sore gums.
• Gum pain: Sore and sensitive gums can make a baby more irritable than usual.
• Increased saliva: From around four months old, babies bite, chew, and drool more. Teething can also increase drooling.
• Facial rash: The extra drool caused by teething can irritate your baby's skin and cause a rash.
• A slight rise in temperature: A slight increase in temperature may accompany teething, but a temperature over 100.4°F (38°C) is considered a fever and is not caused by teething.
• Mucus in the stool: Teething can irritate the intestines, resulting in excess mucus in the stool.

Treating Teething Pain

• Rub your baby's gums with a clean finger or a washcloth dipped in cold water.
• Provide your baby with a chilled teething toy, cold spoon, or chilled fruit in a mesh feeder.
• If your baby seems unable to cope with the pain (e.g., lots of tears), you can give them over-the-counter pain medication for infants. Teething doesn't typically cause severe pain, so if your baby is extremely irritable for more than a day or two, contact your doctor.

Note: Avoid teething tablets, topical gels, and homeopathic remedies, as these are not necessarily effective and may be dangerous.

When to Call a Doctor

Contact your doctor if:

• Your baby has had diarrhoea for longer than two weeks.
• There is blood in your baby's stool.
• Your baby has had a fever for more than two to three days.
• Your baby is losing a significant amount of weight (5% or more of their baseline weight).
• Your baby is dehydrated.
• Your baby seems listless, limp, or unresponsive, or has lost their usual spark.

Food sensitivity

The smell of a newborn's poop can be an indicator of their health and growth status. While a sour-smelling stool is common in newborns, it can also be a sign of a digestive disorder or an intestinal infection.

If your baby is sensitive to lactose, they may also experience gas, diarrhea, and bloating. This sensitivity could be due to the lactose in the milk or other dairy products they are consuming directly or through breast milk if the mother has consumed dairy.

If you suspect your baby is sensitive to certain foods, it is important to consult your doctor, especially if there is a family history of food allergies. They can advise you on dietary changes, such as cutting out dairy products or changing formulas, to help improve your baby's digestion and reduce the occurrence of sour-smelling stools.

Frequently asked questions