There are three reasons why the mouth keeps blistering: 1. It could be herpes labialis, which is caused by herpes simplex virus, and normally requires antiviral treatment, while the surface can also be coated with antiviral drugs, commonly used drugs are acyclovir, valacyclovir, and ribavirin. For the oral surface, under normal circumstances need to maintain oral hygiene. 2, blistering in the mouth, may be caused by traumatic blood blister, usually the mouth has a sharp tooth tip, residual root, residual crown, bad restorations and other long-term stimulation of the mouth, may produce the phenomenon of blood blister, it is recommended that timely repair and repair restorations. 3, the mouth is always blistering, may be due to lip biting, lip licking and other bad habits caused by the possibility of mucus gland cysts. And this mucus gland cysts, generally after the rupture will grow flat, but will recur again, so it is usually recommended to surgically remove the mucus gland cysts, and to ensure the cleanliness of the wound, and to correct bad habits, in order to avoid recurrence.