Level 1: Causes of baby diarrhea There are many causes of baby diarrhea, common ones include infectious diarrhea, food allergies, indigestion, intestinal diseases, etc. Among them, infectious diarrhea is the most common type, usually caused by bacteria, viruses, etc. Food allergy is diarrhea caused by a baby\’s allergic reaction to certain foods. Indigestion may be due to the baby\’s digestion not being fully developed, or eating too much or not eating the right food.