Breastfed babies with diarrhea may be caused by lactose intolerance, poor quality of breast milk and limited digestive ability. 1. Lactose intolerance: babies may lack the enzyme lactase that digests lactose, so lactose intolerance occurs. Especially after eating dairy products, abdominal pain, bloating, diarrhea and other symptoms will occur, so the baby will have diarrhea after eating breast milk. 2. Poor quality of breast milk: The quality of milk produced is poor due to the irrational dietary structure of the mother. Babies may have diarrhea after eating bad quality breastmilk. 3. Limited digestive ability: Due to the limited digestive ability of the baby, if the breastmilk consumed exceeds the body’s tolerance, diarrhea may occur. If a breastfed baby develops diarrhea, parents are advised to take the baby to the hospital to find out the cause of the problem and treat it promptly.