A blood blister in the mouth may be related to physiologic factors such as diet and lifestyle, as well as pathologic factors such as oral ulcers, traumatic blood blisters, and thrombocytopenic purpura. 1.Physiological factors: (1) Diet: daily consumption of overheated and rough food leads to damage to the oral mucosa, resulting in capillary rupture, leading to the appearance of a blood blister in the mouth. (2) Life: daily often late to bed, stay up late, resulting in poor mental state, or even anxiety, irritability, etc., may lead to the emergence of a blood blister in the mouth. 2. Pathological factors: (1) Mouth ulcers: mainly caused by genetic factors, digestive system diseases, endocrine diseases, excessive stress, endocrine disorders, etc., may lead to the appearance of a blood blister in the mouth. (2) Traumatic blood blisters: mainly caused by eating, biting, external contusion to the mucous membrane of the cheek and tongue, which may lead to the appearance of a blood blister in the mouth. (3) Thrombocytopenic purpura: mainly caused by immunity, heredity and primary diseases, which may lead to the appearance of a blood blister in the mouth. Therefore, a blood blister in the mouth should be taken seriously and timely medical examination should be conducted to avoid aggravation of the symptoms.