Infants with sour stool with mucus need to consider lactose intolerance, milk protein allergy, intestinal infections and other causes, need to target the cause of the treatment. 1. Lactose intolerance: Lactose intolerance in infants can lead to prolonged diarrhea, stools can have a sour odor, sometimes with mucus, bloating and nausea and other discomforts. You can try to supplement lactase preparation orally before breastfeeding; if you are formula-fed, you can consider replacing lactose-free milk powder, and then slowly switch back to regular milk powder when the stools return to normal. 2. Milk protein allergy: In addition to sour stools with mucus, sometimes combined with vomiting, bloating, rash, blood in the stool, anorexia and other one or two manifestations. Under the guidance of the doctor, you can replace the deeply hydrolyzed protein milk powder or amino acid milk powder, and follow the principle of adding supplemental food from thin to thick, from a single to a variety, from fine to coarse. 3. Intestinal infections: diarrhea with foul-smelling stools, visible mucus, may be combined with fever, to pay attention to intestinal infections. Need to test the stool to find the pathogen, determine whether it is a viral or bacterial infection after targeted treatment. Infants with changes in stool characteristics, especially loose stools, foul smell, blood, abnormal color, need to consult a doctor in time, after a clear diagnosis for targeted treatment.