1. Causes of diarrhea in five-month-old babies 1.1 Dietary reasons 1.2 Digestive problems 1.3 Viral infection 1.4 Use of antibiotics and other drugs 1.5 Drinking unclean water or food A five-month-old baby may have diarrhea due to a variety of reasons. Diet may be an important reason, such as overfeeding, improper addition of complementary foods, etc. In addition, digestive problems may also cause diarrhea, such as gastroenteritis, enteritis, etc. Viral infections are also one of the common causes of diarrhea, such as rotavirus, adenovirus, etc. use