Lip blisters are clear, fluid-filled mucosal protrusions that occur on the mucous membrane of the lips. This lesion is very common. When these small lip glands are damaged, the saliva flows out into the submucosa and forms small blisters like water sacs, which are called “mucus cysts” in dentistry. Therefore, lip biting is the most common cause of lip blisters. Some patients have uneven teeth, and the tips of the teeth often stimulate the local lip mucosa, which may also form small bubbles on the lips. These small mucous cysts are not serious, but they do not disappear on their own, often deflate after the saliva flows out after breaking, and gradually increase in size after the mucosa heals. Therefore, the best way is to have the cysts removed by an oral surgeon under local anesthesia, which is minimally invasive and does not affect the appearance. In addition, it is important to stop the bad habit of lip biting to avoid new mucous cysts. In the case of blisters on the outside of the lips, they are often caused by the herpes simplex virus. This virus is latent in the patient’s body and attacks the tissues when the immunity is low and the body is in poor condition, causing herpes. You can apply acyclovir cream or other antiviral medications and pay attention to adjusting your body condition.