The purple-black color of the tongue may be caused by eating black-purple food, or it may be caused by tongue trauma, hemangioma and other diseases. 1. Eating black and purple food: If you eat a lot of black and purple food such as mulberry, black wolfberry, etc., it may lead to tongue coloring, thus appearing black and purple tongue, which is a normal physiological phenomenon and doesn’t need to be treated. 2. Tongue trauma: when the tongue is bitten or touched, it may lead to blood circulation obstacle in the tongue area, and then the patient will have the performance of tongue bruise and swelling. 3. Hemangioma: the cause of hemangioma is still unclear, and it is considered to be related to the abnormal transformation of endothelial cells, disease-causing gene mutation and other factors. If hemangioma occurs in the patient’s tongue, it may be manifested as purple-black or dark-red patches. It is recommended that patients with purple-black tongue need to consult a doctor in time, if it is caused by physiological factors, no treatment is needed. For diseases that cause purple-black tongue, it is necessary to choose the appropriate measures for the cause of treatment.