Level 1: Causes of diarrhea in half-year-old babies: Half-year-old babies are prone to diarrhea because their digestion is not yet complete. Diarrhea may be caused by food allergies, viral or bacterial infection, indigestion, etc. Breastfed babies have less diarrhea, while bottle-fed or mixed-fed babies may be more likely to have diarrhea. Level 2: How to judge whether a half-year-old baby has diarrhea. How to judge whether a half-year-old baby has diarrhea.