The reason why babies have diarrhea when they eat milk is because of lactose intolerance or indigestion. 1. Lactose intolerance: Because breast milk or some formula contains lactose, infants with lactose intolerance will experience diarrhea, bloating and other symptoms, and need to eliminate the triggering factors in a timely manner, to reduce the intake of lactose, you can feed lactose-free milk powder. 2. Indigestion: Due to the relatively weak digestive function of infants, when improper care is prone to the above symptoms. It is recommended that local hot compresses and massages be used to regulate the situation, and if necessary, follow the doctor’s instructions to take Bacillus subtilis bacillus granules to alleviate the problem and promote early recovery. The baby is not only a baby, but also may have other reasons, it is recommended to go to the hospital, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.