The presence of black blood blisters in the oral cavity cannot be broken by oneself, and need to go to the hospital and be treated by a professional doctor. There are blood bubbles in the oral cavity, usually in the process of chewing to the oral mucosa, but did not bite through the oral mucosa, so that the capillaries under the mucosa rupture and form a small amount of bleeding, bleeding retained in the oral mucosa, will form a small blood bubble. Some people have higher blood pressure or poorer blood clotting mechanism, the blood bubble will gradually increase in size, to a certain extent will rupture. Black blood vesicles in the mouth may also be the result of eating too hot, too hard food, and the mucosa is subjected to strong friction and produce blood vesicles. At first, there is fresh blood inside the vesicles, and then they gradually turn black. In addition, blood vesicles in the mouth may also be hemangioma caused by vascular malformation, which can be treated by local injection of sclerosing agent to promote the regression of blood vesicles, or choose to undergo surgical excision. Patients should pay attention to oral hygiene, chew slowly and avoid spicy food to prevent the oral mucosa from being damaged again.