If the inside of the lips blistered there are three possibilities: First, blood blisters, that is, caused by accidental bites. This time does not need to take any treatment measures, in about 2 days will be automatically absorbed. Second, transparent blisters, if it is transparent blisters, may be caused by herpes virus infection, usually in about a week will also heal. You can take oral acyclovir for antiviral treatment, and after the blister breaks, spray some local open throat sword spray to promote the healing of the broken surface. Third, there may be a hard white blister inside the lips, and it lasts for a long time, usually not disappearing automatically in about one or two months. This is a small mucus cyst, which usually needs to be treated by surgical removal.