Dark tongue color may be caused by dark-colored food, bacterial infection, endogenous coloring and so on. 1. Dark-colored food: dark tongue is not necessarily caused by disease, but may be food coloring, such as eating dark chocolate, mulberry and other dark-colored food, which can also lead to the phenomenon of dark tongue. 2. Bacterial and fungal infections: when the patient’s body resistance decreases, poor oral hygiene, etc., it is easy to cause oral flora disorders, resulting in bacterial infection of the tongue and dark tongue color. 3. Endogenous coloring: If the patient suffers from hemangioma, melanoma and other diseases, the phenomenon of dark tongue may occur. Patients with dark-colored tongue should go to the hospital in time, after clarifying the cause of the disease, and then give the correct treatment and therapy under the guidance of the doctor.