Some potential causes of blood in baby's stools:
* A common cause of blood in an infant's stool is a slight anal tear (fissure) from baby straining with the passage of the stool. The small amount of blood from an anal fissure tends to look like a red streak on the outside of the stool.
* Another common cause of blood in the stools of infants is food allergies. The top allergens are cow's milk products and soy. See Dairy and other Food Sensitivities in Breastfed Babies for more information.
* A third common cause: If mom has a cracked nipple or other bleeding, then baby may ingest some blood from mom (this is not harmful to baby), which may show up in baby's stool.
* Occasionally, blood in the stool may be due to breastmilk oversupply. Per Dr. Jack Newman, bloody stools in some babies have been eliminated completely by resolving mom's oversupply. This can be done by following the usual management procedures for oversupply; it can also be helpful to use breast compressions to increase the amount of fat that baby gets while nursing. See Can a baby be allergic to breastmilk? for more information on oversupply causing blood in baby's stool.
* There are several case reports of a baby beginning to have mucous and/or blood in the stool after starting vitamin/fluoride drops, where the blood disappeared after the drops were discontinued.
* Blood in the stool may also be caused by a temporary case of lactose intolerance, due to an intestinal infection.
* Certain kinds of infectious diarrhea can cause bloody stools in babies, including Salmonella and C. Difficile. C. Difficile is a bacteria that grows in the gut if the bacterial balance has been upset; the toxin can cause injury to the mucosa and bloody stools. Breastfed babies tend to have less severe symptoms than non-breastfed babies because breastmilk inhibits the growth of the bacteria.
* Various forms of colitis, intussusception, or other intestinal disorders are other possible causes.