Oral blisters are mainly due to the following reasons: first, if the oral mucosa at the blood blisters, most of them are caused by dental bite. For example, the presence of misplaced teeth in the mouth, the sharp tip of the teeth, can often bite the mucous membrane on the cheek side, this bite is very strong, it is easy to cause the mucous membrane blood blisters, if the blood blisters are not big, most of them can be absorbed on their own without special treatment, if the blood blisters are very large, you need to go to the hospital in the doctor’s strict disinfection, will be blisters picking, discharging pus and blood. Second, the oral cavity has chronic periapical inflammation or periodontal inflammation, blood blisters are located in the mucosa of the gums, due to periapical inflammation will make the mucosa of the apical area of the tooth red, swollen, pressure and pain, when the periapical area of the pus is more, will make the mucosa appear pustules, or fluctuation of the pustules of the strong sense, in this case, we need to do the root canal treatment of the tooth in order to control the inflammation.