Baby’s fever and diarrhea may be caused by acute gastroenteritis, acute upper respiratory tract infection, pneumonia and other reasons. 1. Acute gastroenteritis: usually the baby in daily life, if not pay attention to dietary hygiene, may stimulate the gastrointestinal tract, resulting in acute gastroenteritis, thus appearing fever and diarrhea. 2. Acute upper respiratory tract infection: usually after a baby catches a cold, bacteria and viruses will invade the body, affecting the peristaltic function of the gastrointestinal tract and reducing the ability to digest and absorb. Therefore, there will be fever and diarrhea. 3. Pneumonia: usually after some babies pneumonia, the inflammation of the lungs aggravated, inflammation stimulation of the gastrointestinal tract, may lead to indigestion, resulting in fever and diarrhea. If your baby has a fever and diarrhea, it is recommended that you seek medical attention to determine the cause of the illness and to get the relevant treatment.