Breast milk is the best food for infants and young children, so it is generally recommended to exclusively breastfeed for 6 months, and then add complementary foods after 6 months. Breastfeeding diarrhea is mostly seen in small infants within 6 months of age, generally soon after birth, diarrhea occurs, the stool is mostly foamy and thin watery, sometimes containing milk flaps, occasionally green, also with strips of transparent mucus, the smell has a special sour odor. The stools are usually frequent, ranging from 3 to 20 times a day. The causes of diarrhea in babies eating breast milk may be the following: 1, the prostaglandin content in breast milk is high, the substance promotes the smooth muscle movement of the small intestine, increasing the secretion of water and electrolytes and produce thin stools, the infant organism will gradually adapt to the prostaglandin in breast milk. 2, the baby is intolerant to lactose, the body lacks lactase. Such babies can be consumed in small amounts several times to reduce the lactose intolerance reaction, each time the amount of consumption should not exceed 250ml, also can be fed low lactose milk or rice soup, can make the baby lactose intolerance situation is greatly relieved, as the baby grows, lactase will also gradually mature, enzyme activity is enhanced, and then decomposition, digestion and absorption of lactose. 3, pay attention to the mother’s diet, if the mother often eat more oil, high fat, stimulating food, resulting in the milk contains more ingredients than the baby needs, it will make the baby diarrhea. In addition, the mother’s diet needs to pay attention to the baby’s allergies to food. For example, if the baby is allergic to milk, eggs, seafood, wheat, etc., then the mother will also experience increased diarrhea and even blood in the stool if she eats these foods, and some babies will have significant eczema. If the mother’s diet adjustment is still not enough to improve the baby’s diarrhea, she can give her baby some lactase to help digest the lactose in breast milk. In conclusion, mild cases of physiological diarrhea in newborns do not require treatment and can continue to be nursed, so that the lactase enzyme will gradually develop and mature, the enzyme activity will increase, and gradually be able to break down, digest and absorb lactose, which will gradually improve with the addition of complementary foods. However, if the baby has sudden onset of diarrhea within a short period of time, the number of stools increases significantly or contains mucus and pus and blood. At the same time, the child has a significantly reduced appetite, frequent vomiting, reduced urine output, frequent crying, fever, poor weight gain, and eczema, which are considered to be other causes of diarrhea and require prompt medical treatment.