Key takeaways: Common causes of blood in a baby’s stool include small anal tears from hard stools, swallowed blood from cracked nipples, and allergic proctocolitis from cow’s milk protein. Less often, it signals infection or a serious bowel problem. Always call your baby’s doctor, and seek urgent care if your baby seems sick, vomits, or has a swollen belly.
Seeing blood in a diaper is alarming. Many causes are mild, but it always deserves a call to your doctor.
Common Causes
Anal fissure: a small tear from passing a hard stool. Causes streaks of bright red blood on the stool.
Swallowed blood: babies may swallow blood from cracked nipples during breastfeeding or from a nosebleed. This can show up as dark or black stool or in spit-up.
Allergic proctocolitis: a reaction to proteins, most often cow’s milk protein, in formula or passed through breast milk. Babies typically:
- Have streaks of blood and mucus in the stool.
- Otherwise seem well and are growing.
- Often improve when the protein is removed from the diet, under medical guidance.
Infection: some bacterial infections cause bloody diarrhea, often with fever.
From the author
From First Breath to First Birthday is my month-by-month guide to your baby’s first year, written as a NICU and postpartum nurse. My book covers common first-year illnesses and the warning signs that mean it’s time to call the doctor, explained the way I’d explain them at the bedside.
Less Common but Serious Causes
- Intussusception: bloody, jelly-like stool, severe crying, vomiting, sleepiness.
- Necrotizing enterocolitis (NEC): mostly in preterm babies in the NICU.
- Volvulus: twisting of the bowel, often with green vomiting.
Things That Look Like Blood
- Red foods or drinks, such as beets or red-colored products.
- Some medicines.
- Urate crystals in newborn diapers (orange-pink dust in urine).
Save the diaper or take a photo to show the doctor.
Get emergency care if your baby: has a lot of blood in the stool, vomits (especially green), has a swollen or hard belly, is very sleepy or hard to wake, has severe crying bouts, or seems very unwell. Call your doctor for any blood in the stool.
The Bottom Line
Blood in the stool is often from a minor tear, swallowed blood, or milk protein allergy, but it always needs a call to the doctor.
Want more support for your baby’s first year? My book, From First Breath to First Birthday, is available on Amazon.
Related Articles
- Mucus in Baby’s Stool
- Intussusception: Warning Signs of a Bowel Emergency
- Breast Milk Colors: What’s Normal
Sources
- American Academy of Pediatrics. Blood in the stool. HealthyChildren.org. https://www.healthychildren.org
- Koletzko S, Niggemann B, Arato A, et al. Diagnostic approach and management of cow’s-milk protein allergy in infants and children: ESPGHAN GI Committee practical guidelines. J Pediatr Gastroenterol Nutr. 2012;55(2):221-229.
- Lawrence RA, Lawrence RM. Breastfeeding: A Guide for the Medical Profession. 9th ed. Elsevier; 2022.
This article is for general education and is not a substitute for individualized medical advice. Always talk with your baby’s health care provider or your own provider about your specific situation. If you think your baby or you may have a medical emergency, call 911.
