Infants have diarrhea when they eat breast milk, the main consideration is the existence of breast milk diarrhea, which may be due to excessive prostaglandins contained in breast milk, infants intolerance to lactose and other reasons. 1. Excessive prostaglandins: prostaglandins have the function of promoting gastrointestinal motility, and infants who consume breast milk containing too many prostaglandins will have their gastrointestinal motility increased, causing diarrhea. 2. Lactose intolerance: when infants are lactose intolerant, the lactose in breast milk cannot be fully digested after it is ingested into the infant’s body, causing increased intestinal emptying and diarrhea symptoms. Babies eat breast milk on diarrhea, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.