There are several reasons for blisters inside the lower lip: 1. mucus gland cysts, there are several mucus gland glands inside the lower lip, this small gland is also used to secrete saliva, so it is easy to produce trauma when inadvertently biting the lip, resulting in blockage of the salivary gland ducts, it is easy to appear salivary gland cysts. This small cyst can be treated by outpatient surgery and requires local medication, if the cyst is relatively large, you can wait for it to gradually subside and then remove it when it is smaller. 2, it may also be caused by herpes virus, in this case, anti-viral treatment is needed, often using drugs such as virazole and acyclovir, and at the same time to improve the body’s resistance. 3, there may also be due to burns The surface can be coated with medication to promote healing, such as tin or corticosteroid.