Blisters on the lower lip may be herpes labialis caused by herpes simplex virus infection, or mucous gland cysts. Herpes labialis occurs on the red edge of the lips or in the corner of the mouth area, often recurring in the same location, starting with clusters of small blisters, slowly breaking into patches, oozing and crusting, healing in about a week, the onset of which requires systemic antiviral therapy, oral acyclovir 200mg orally, 5 times a day for 5 days for a course. Topical antiviral treatment, such as applying acyclovir ointment on the affected area. Blistering of the lower lip may also be a manifestation of mucous gland cysts. Mostly seen in the inner mucosa of the lower lip, which is rich in small mucus glands, unconscious lip biting or mechanical stimulation may trigger cysts of mucus glands. And it is easy to recur, and there will be obvious discomfort when the cyst appears. Sometimes small cysts can disappear on their own, and those that cannot disappear on their own need to be removed completely by surgery to avoid recurrence. Therefore, most of the blisters on the lower lip are symptoms of herpes simplex virus, but they may also be caused by small cysts in the mucus glands.