Nine-month-old baby diarrhea that is diarrhea, may be related to infection, allergies, etc., need to follow the doctor’s instructions to rehydration, the use of bifidobacterium bifidum, cefotaxime, to avoid contact with allergens, etc. to alleviate diarrhea. 1. Infectious diarrhea: may be related to rotavirus, diarrhea-causing Escherichia coli and other infections. In viral infections, symptomatic treatment: rehydration to prevent electrolyte disorders, probiotics (bifidobacteria) to regulate intestinal flora, montelukast to protect the intestinal mucosa to stop diarrhea. In case of bacterial infection, antibacterial drugs such as cefotaxime should be added. 2. Allergic diarrhea: baby allergic to certain foods can also cause diarrhea, can be accompanied by abdominal pain, vomiting and other symptoms, should be avoided to use allergic foods, if it is allergic to milk protein and other allergies, but also need to change the type of milk powder, such as the use of free amino acids or hydrolyzed protein formula. Nine-month-old babies may have other causes of diarrhea, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment. The above medications should be used under the guidance of a doctor.