The color of stools of three-month-old babies should be yellow and streaky which is normal, but there are exceptions. If the baby is formula-fed, the stool may be green because of more iron in the formula, but if it is persistently green, with good mental status and good weight and height, then it can be closely followed up and observed, and if bloating, diarrhea, bloody stools, etc. occur, consult a doctor promptly. However, if the baby has dilute watery stools or egg-shaped stools, we should be alert to enteroviral infections, such as rotavirus, norovirus and other infections. You can follow the doctor’s instructions to be montelukast, intravenous rehydration and other symptomatic supportive treatment. In addition, lactose intolerance food protein allergy caused by enteritis, because often manifested as abdominal distension and blood in the stool. You can switch to moderately hydrolyzed milk powder or deeply hydrolyzed milk powder to feed under doctor’s guidance. If your baby has blood, mucus, pus and blood in the stool, you should seek medical attention and follow the doctor’s instructions for targeted treatment.