Red or Bloody Baby Poop

Seeing red in your baby's diaper sends an immediate jolt of adrenaline through your body. That is a completely normal reaction. But here is the reassuring truth: the vast majority of blood in baby stool has a minor, treatable cause. The most common culprit — by a wide margin — is a tiny anal fissure, which is essentially a paper cut near the anus caused by passing a firm stool. It looks scary but heals quickly.

That said, blood in a diaper is never something to simply ignore. The critical skill is knowing the difference between something that can wait for your next pediatrician visit and something that requires immediate medical attention. This guide gives you a clear framework for making that call.

One important note before we go further: white, pale, or chalky stool is always an emergency regardless of whether blood is present. If you ever see stool that is the color of white clay or putty, contact your pediatrician immediately. That indicates a potentially serious liver or bile duct condition. See our guide on white or pale baby poop for more details.

If you see a bright red streak of blood on the surface of a firm stool — sitting on top of it, not mixed in — an anal fissure is the most likely explanation. An anal fissure is a small tear in the delicate skin around the anus, usually caused by passing a hard or large bowel movement. Think of it as a tiny paper cut in a sensitive area.

Anal fissures are extremely common in infants. They happen in both breastfed and formula-fed babies, though they are more frequent in formula-fed babies and babies who have started solids, simply because their stool tends to be firmer. You might also notice your baby straining, grunting, or crying during bowel movements — not because of the fissure itself, but because of the hard stool that caused it.

The blood from a fissure is typically bright red because it is fresh — it is coming from the surface of the skin right at the exit point, so it has not been digested or altered. You may see it as a streak on the stool, a small smear on the diaper, or a tiny spot on the wipe.

The good news: anal fissures heal quickly, usually within days, once the underlying constipation is addressed. The key is softening the stool so the fissure is not re-opened with each bowel movement.

In the first two to three days of life, dark blood in a newborn's stool or spit-up may actually be the mother's blood, swallowed during delivery or from cracked nipples during breastfeeding. This is surprisingly common and completely harmless to the baby.

The blood can appear dark red, brown, or even black because it has been partially digested in the baby's stomach. It can look alarming — especially mixed with meconium, which is already dark and tarry — but it does not indicate any bleeding inside the baby.

If there is any question about whether the blood is maternal or the baby's own, your hospital or pediatrician can perform an Apt test (also called the Apt-Downey test). This simple lab test distinguishes between fetal hemoglobin and adult hemoglobin, quickly confirming the source. If the blood is maternal, no treatment is needed. If a breastfeeding mother has cracked or bleeding nipples, treating the nipples with lanolin cream and working with a lactation consultant to improve the latch will resolve the issue.

Cow's milk protein allergy is the second most common cause of blood in infant stool, affecting roughly 2-3% of babies according to the American Academy of Pediatrics. It occurs when the immune system reacts to proteins found in cow's milk — and it can happen in both formula-fed babies (who are directly consuming cow's milk protein) and breastfed babies (who receive traces of it through the mother's diet).

The blood from CMPA looks different from fissure blood. Instead of a streak on the outside, you typically see small flecks or threads of blood mixed into the stool itself, often accompanied by mucus. The stool may be loose, greenish, or have a stringy, mucousy quality. CMPA blood is the body's inflammatory response to the protein — the intestinal lining becomes irritated, and small amounts of blood seep through.

CMPA often comes with a cluster of other symptoms beyond stool changes. Your baby may have eczema or persistent skin rashes, seem uncomfortable during or after feeds, have excessive gas, or show signs of reflux. Not every fussy, gassy baby has CMPA — those symptoms are also just normal newborn life — but when you see the combination of blood or mucus in stool plus skin issues plus persistent feeding discomfort, it is worth discussing with your pediatrician.

Diagnosis typically involves an elimination trial. For formula-fed babies, your pediatrician may recommend switching to an extensively hydrolyzed formula like Nutramigen or Alimentum, where the cow's milk proteins are broken down into tiny fragments that the immune system does not react to. For breastfed babies, the mother may be asked to eliminate all dairy from her diet for 2-4 weeks to see if symptoms improve. Resolution of symptoms confirms the diagnosis.

Once babies start solids — typically around 6 months — a whole new category of colorful diapers enters the picture. Red or reddish stool is frequently caused by foods, not blood. Beets are the most famous culprit, capable of turning stool (and urine) a startling shade of crimson. Sweet potatoes, tomatoes, cranberries, red peppers, and red gelatin can also add a reddish tint. Artificial red food coloring, found in some children's medications and juice drinks, is another common cause.

If your baby recently tried a new red or deeply colored food and you see a reddish diaper with no other symptoms — no pain, no fever, no change in behavior — dietary pigments are the most likely explanation. The color should clear within a day or two after the food passes through the system.

When in doubt, your pediatrician can perform a simple guaiac test (also called a fecal occult blood test) on a stool sample to determine whether actual blood is present. This takes the guesswork out of the equation entirely.

Most blood in baby stool does not require an ER visit. But there are specific scenarios where immediate emergency care is critical. Knowing these ahead of time means you will not hesitate when it matters.

The most urgent scenario is stool that resembles dark red currant jelly or raspberry jam. This is a hallmark sign of intussusception — a condition where one section of the intestine telescopes into another, cutting off blood flow. Intussusception most commonly occurs in babies between 6 months and 3 years old and typically presents with episodes of severe, colicky abdominal pain (baby draws knees to chest and screams), vomiting, and then the characteristic jelly-like bloody stool. This is a true surgical emergency, and outcomes are excellent when treated quickly — usually with an air or barium enema to unfold the intestine, or surgery if needed.

Large volumes of blood, signs of shock (pale or gray skin, limpness, rapid breathing, weak cry), or a rigid and distended abdomen also warrant an immediate ER visit. Trust your instincts — if your baby looks seriously ill, act first and sort out the details later.

One of the most important things your pediatrician will ask is where the blood is relative to the stool. This detail helps narrow down the cause considerably.

Blood on the outside of the stool — sitting on the surface, smeared on the diaper, or visible only when you wipe — almost always comes from the very end of the digestive tract. The anus, the rectum, or the very last part of the colon. Anal fissures are the top cause here. The blood is bright red because it is fresh and undigested.

Blood mixed into the stool — flecks, threads, or a uniform reddish or maroon color throughout — suggests the source is higher up. It may be coming from the colon (as with CMPA-related colitis or an infection) or even higher in the GI tract. Blood that has traveled through part of the digestive system gets partially digested, which is why it may appear darker or mixed uniformly rather than sitting on the surface.

Black, tarry stool (outside of the newborn meconium period) is the most concerning pattern. Called melena, it indicates that blood has been fully digested — meaning the bleeding source is in the stomach or upper small intestine. Melena in an infant beyond the first few days of life requires prompt medical evaluation.

When in doubt, take a photo. A picture of the diaper gives your pediatrician far more information than a verbal description over the phone, and it captures details you might not remember later.

Blood in your baby's diaper is startling, but in most cases, the cause is something minor and manageable — usually an anal fissure from a hard stool or a dietary pigment that mimics the look of blood. Cow's milk protein allergy is the next most common cause and is treatable with a formula change or maternal dietary elimination.

The key is knowing the red flags that require urgent action: large volumes of blood, dark jelly-like stool, signs of severe illness, or a rigid abdomen. If you see any of those, go to the emergency room without delay. For everything else, document what you see — a quick photo and a note in your diaper log — and call your pediatrician for guidance.

Tracking your baby's diapers over time with an app like tinylog gives you and your doctor the context to tell whether a bloody diaper is an isolated event or part of a pattern. That information is what turns a worried phone call into a productive conversation.

• Baby Poop Color Chart — What every color means
• Dark or Black Poop — When dark poop is normal and when it is not
• Mucus in Poop — What mucus means and when to see your pediatrician
• Milk Protein Allergy in Poop — Signs of allergy in your baby's diaper

• American Academy of Pediatrics (AAP). (2023). Blood in Infant Stool. HealthyChildren.org.
• Vandenplas, Y., et al. (2019). Guidelines for the diagnosis and management of cow's milk protein allergy in infants. Archives of Disease in Childhood, 92(10), 902-908.
• NASPGHAN. (2023). Approach to Rectal Bleeding in Infancy. North American Society for Pediatric Gastroenterology, Hepatology and Nutrition.
• Heine, R. G. (2018). Cow's milk protein allergy in infancy: A review of current concepts. Journal of Paediatrics and Child Health, 54(12).
• Applegate, K. E. (2009). Intussusception in children: Evidence-based diagnosis and treatment. Pediatric Radiology, 39(Suppl 2), S140-S143.
• CDC. (2024). Infant and Child Nutrition: Introducing Solid Foods. Centers for Disease Control and Prevention.

This guide is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Blood in your baby's stool should always be evaluated by a healthcare provider. If your baby appears seriously ill or you see signs of an emergency described in this guide, seek immediate medical attention.