Diarrhea does not usually cause toothache. Diarrhea is usually caused by digestive diseases, such as intestinal inflammation, increased intestinal osmotic pressure, etc. Toothache is usually caused by oral diseases, such as caries, pulpitis, etc., as follows. 1. Diarrhea: Infectious enteritis, inflammatory bowel disease caused by bacteria, viruses, fungi, etc., as well as drugs or food causing increased intestinal osmotic pressure and other diseases may lead to diarrhea. 2. Toothache: when deep caries occurs, food or cold water into the cavity will cause toothache; when pulpitis occurs, the affected teeth may have spontaneous pain, and the pain can be triggered or aggravated by hot and cold stimuli. If the above symptoms occur, it is recommended to go to the hospital in a timely manner, and receive targeted treatment as soon as possible.