Clear blisters on the inner wall of the lower lip may be related to mucous gland cysts, herpetic stomatitis, herpetic mouth ulcers and other causes. 1. Mucous gland cysts: the secretion of mucous glands is blocked due to local trauma, duct obstruction and other factors, causing a clear blister on the inner wall of the lower lip. 2. Herpetic stomatitis: related to herpes simplex virus infection, usually in the early stage of the onset of a single blister or more blisters fusion manifested as a single. 3. Herpes oral ulcers: oral mucosa extensive congestion, edema, small blisters will appear inside the mouth, with the development of the disease, small blisters rupture to form ulcers. It is recommended that people with transparent blisters on the inner wall of the lower lip go to the hospital in a timely manner to clarify the cause of the disease and standardize the treatment under the guidance of the doctor.