Blood blisters in the mouth are often called mouth sores, and sometimes these sores, also known as mouth ulcers, can have a recurrent pattern of change. Another condition is that the blisters are related to traumatic factors, such as mechanical injuries, such as hard objects or toothbrushes, which can damage the oral mucosa and lead to the formation of blisters in the mouth. In addition, like chemical damage, such as drugs, aspirin or tincture of iodine and other irritating drugs, may cause local oral mucosa damage. Physical stimulation, such as too hot water, food, may cause mucosal damage. Or inside the mouth to do special cryotherapy, such as liquid nitrogen treatment, improper operation may also cause oral blood blisters. In addition, some diseases can be accompanied by oral blood blister changes, such as leukoplakia, tumors, etc.