Purple tongue may be caused by food coloring, tongue injury and hemangioma. 1. Food coloring: If you eat food containing anthocyanin, the purple color of tongue will appear, such as purple potato, mulberry and so on. 2. Tongue injury: If you bite your tongue accidentally or get impacted by external force, it will easily cause congestion and swelling of the tongue, and a large amount of blood stagnation may lead to purple color of the tongue. 3. Hemangioma: the appearance of hemangioma on the patient’s tongue will be accompanied by the enlargement of the hemangioma, which will invade the surrounding tissues and blood vessels, resulting in the compression of the tongue tissues, and the symptom of purple tongue will appear. When the patient’s tongue appears purple and accompanied by physical discomfort, it is recommended to go to the hospital stomatology department in time for examination and treatment according to the cause of the disease.