Blood in baby’s stool is commonly caused by the following reasons, one, the mother’s nipple breaks and bleeds. During breastfeeding, especially in the early days, the mother’s nipple can easily break down. If the baby swallows the blood from the mother’s nipple break down, the stool will have a small amount of pink or red material. Second, took iron supplements. If your baby takes iron-containing multivitamin preparations or iron-supplementing drugs, it is unlikely that all of the iron will be absorbed and a small amount will be excreted through the intestines. At this time, the stool may contain a dark brown material. Third, the mucous membrane of the small intestine is damaged. If the mucous membrane of the small intestine is damaged, the stool will also have red substances and the stool test will be positive for occult blood. IV. Anal fissure. If fresh blood is visible in the stool and the blood adheres to the surface of the stool, and the examination suggests red blood cells, it is most likely due to anal fissure. The baby will be accompanied by crying and straining to defecate, but the stool is not necessarily dry. Because the baby’s anal sphincter is not mature enough, contraction and diastole are not well regulated, and there are often small fissures caused by the defecation process, resulting in small amounts of blood in the stool. This is when a small amount of ointment containing antibiotics is applied to the anus.