If you have a clear blister in your mouth, you should identify what causes it: 1. If it is a clear blister on the internal mucosa of the lip caused by bad lip biting habits, consider it to be a mucus gland cyst, and you can choose surgical removal treatment, and quit bad habits, do not often bite your lips, lick your lips, to avoid recurring attacks. 2. If it is a series of small clear blisters caused by the herpes virus, you need anti-viral treatment, because There is a self-limiting, without treatment is also able to cure, about 7-15 days to heal, after the blister breaks, there may be pain, will form a scab, you can choose to use to promote healing drugs to promote its rapid healing. Commonly used drugs are acyclovir, valacyclovir, or you can choose to apply acyclovir ointment topically.