Diarrhea in a 3-month-old baby requires general treatment such as changing formula, keeping warm, and medication such as montelukast, depending on the specific situation. Baby diarrhea with milk petals, or a sour smell, may be caused by lactose intolerance, if breastfeeding, you can suspend breastfeeding, if it is ordinary formula feeding, you can try to replace the lactose-free milk powder and so on. If the diarrhea is caused by indigestion due to cold, keep the baby warm and apply warm compresses to the baby’s stomach. If it is not relieved, you can give your baby medicines such as Montelukast and Bacillus subtilis granules under doctor’s guidance. Baby diarrhea at the same time poor state, crying, vomiting and other symptoms, need to go to the hospital in time to do a stool examination, if diagnosed as caused by enteritis, need to follow the doctor’s instructions to take cefaclor suspension, amoxicillin and other drugs treatment. 3 months baby diarrhea may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.