If a white blister is found to form inside the lips, it is likely that a mucus gland cyst is formed. There are small salivary glands underneath the mucous membrane of the lips, and if they are accidentally bitten, they may cause the salivary gland glands to rupture, so that the mucus inside the salivary glands will flow outside and form cysts. When a mucus gland cyst is first formed, it is clear and blister-like. If it does not heal for a long time, the surface will gradually become keratinized, the blisters will gradually become opaque white blisters, and the texture will become harder. At this time, surgical excision is clinically necessary for treatment. When mucous gland cysts are removed, the mucous cyst wall must be completely removed, otherwise it is very easy to recur.