Causes and When To Call the Doctor

As odd as it sounds, you can learn a lot about your little one’s development by looking in their diaper. During your baby’s first few months, you’ll notice plenty of brown, yellow, and green poop—all of which are normal colors for breastfed and formula-fed infants. Occasionally, however, you might notice blood in your baby’s poop, and this can definitely send off the alarm bells.

Rest assured that blood in infant stool—whether it’s small flakes or large streaks—is usually harmless. But in rare cases, it can indicate a medical problem such as an infection or bleeding along the upper gastrointestinal (GI) tract.

Keep reading to learn about the possible causes of blood in baby poop. We also break down symptoms that warrant a visit to the doctor or emergency room.

Common Causes of Bloody Stool in Babies

Baby poop is usually brown, yellow, or green, says Nanci Pittman, MD, a pediatric gastroenterologist and assistant professor of pediatrics at Mount Sinai School of Medicine in New York City. Occasionally you might come across blood in your baby’s stool. Here are the most common causes.

Constipation

Constipation is fairly common in babies, usually coming from a milk protein allergy, starting solids, or not getting enough fluids. Telltale symptoms include a prolonged absence of stool, hard poop that looks like pebbles, fussiness, discomfort, and a firm-feeling belly.

Constipation can also cause tiny tears in the anus (anal fissures), which lead to bloody streaks or flakes on the stool’s surface. These tears happen in the mucosa lining the bottom part of the intestine and around the anus, says Jenelle Ferry, MD, neonatologist and director of feeding, nutrition, and infant development at Pediatrix Medical Group in Tampa, Florida. “Sometimes you can see a small tear if you look closely at the anus, and other times these tears are just inside and not quite visible.”

According to the American Academy of Pediatrics (AAP), anal fissures are the most common cause of blood in a child’s stool. Blood from anal fissures will be bright red, indicating newer blood, says Dr. Ferry.

Most anal fissures heal themselves. “Anal tears should get better in four to six weeks, and healing can be aided by warm baths and diaper ointment,” says Dr. Ferry. If you suspect constipation, consider changing your baby’s diet. For example, you may try eliminating dairy, adding more fiber, and ensuring they’re getting enough fluid. Talk to your doctor for more information on combating constipation.

Infections

Blood in baby poop can also signal certain bacterial infections, including gastroenteritis, salmonellosis, shigellosis, staphylococcal infection, Clostridioides difficile (C. diff) infection, or campylobacteriosis. That’s because infections often cause intestinal inflammation and tiny ruptures that let blood leak out.

Loose stool commonly comes with infections, and so does mucus in the stool, adds Dr. Ferry. If you notice diarrhea with bloody poop, alert your doctor right away. If there is an infection, they might prescribe antibiotics to help treat it.

Food allergies

Food allergies can inflame the colon, allowing blood to trickle into the stool. The most common food sensitivity in babies is to cow’s milk protein. “This is not the same as a lactose intolerance, but a true allergy to a protein (which babies often outgrow),” says Dr. Ferry.

Your baby could also be allergic to other common food allergens, such as soy, eggs, fish, shellfish, tree nuts, peanuts, or wheat. What’s more, breastfed babies can react to something in their lactating parent’s diet.

With food allergies, the blood may be lighter red or often very dark, says Dr. Ferry. Food allergies usually present with other symptoms, too, including skin rashes, vomiting, and diarrhea. Fussiness, colic, or reflux may also be present with a milk protein allergy, adds Dr. Ferry. Your medical provider can help diagnose allergies and develop a treatment plan.

Parental nipple injuries

If a breastfeeding or chestfeeding parent has cracked and bleeding nipples, the baby could swallow some of the blood while nursing, leading to dark red or black flecks in their stool on the way out. This usually isn’t cause for concern, but modifying your baby’s latch can prevent or reduce nipple abrasions and soreness. Contact a health care provider or lactation consultant for assistance in adjusting your nursing technique as needed.

Gastrointestinal tract bleeding

In rare cases, dark red, black, or tarry stool indicates bleeding along the upper gastrointestinal (GI) tract. GI bleeding often comes from a severe illness or injury, so it’s vital to alert your doctor immediately if your baby has dark red or black blood in their poop. One common cause of upper GI bleeding in babies is ulcers, so be sure to check with your doctor.

Urate crystals

Are you seeing an orange-pink chalky substance in your newborn’s diaper? This is likely urate crystals that develop when a baby’s urine is super concentrated—usually in the first few days after birth, says Dr. Ferry. Some parents may mistake urate crystals for blood in the diaper.

Other causes of bloody baby poop

Bloody baby stool can also have less common causes. For example, Streptococcus bacteria could infect the skin around the anus, resulting in inflammation and bloody poop. Colitis (inflammation of the large intestine), Crohn’s disease, or necrotizing enterocolitis can also cause blood in stool. 

Very rarely, the intestine can fold in on itself, resulting in a medical emergency called intussusception. “It causes blockage of the intestine and is often accompanied by severe and sudden cramping pain (usually with intermittent crying), vomiting, and bloody stool with mucus that may look like jelly,” says Dr. Ferry. Late diagnosis can be dangerous, so if you suspect intussusception, see a doctor right away.

When To Call the Doctor About Blood in Infant Stool

With bloody stool in infants, you’ll usually find that your baby is acting normally, and the amounts of blood are small, says Dr. Ferry. Cases like this can be monitored at home, though you should always let the pediatrician know about bloody stool.

“If your baby was born prematurely or with a heart condition and is under 2 months old, it’s a good idea to check in with your doctor. If your baby has bloody stools along with fevers and is acting sick, you should seek immediate care,” advises Dr. Ferry.

Make sure to give the doctor a detailed overview of your baby’s symptoms: Is the blood dark red or bright red? Does it appear as streaks on the outside of the stool, or is it mixed throughout the poop? Does your baby have fever, diarrhea, or other unusual symptoms? Keeping a detailed log will help the health care provider reach a diagnosis.

In the office, the doctor may also analyze your baby’s stool and examine it for signs of infection or illness. Treatment depends on the suspected cause of the bloody stool. Most of the time, though, bloody stool doesn’t result in any long-term health issues.