The most common reason for a layer of white film on the inside of the lips is mouth ulcers, thrush and other diseases, it is recommended that active treatment. 1. Mouth ulcers: when accidentally biting the lips, or lack of iron, vitamin B12 or folic acid and other trace elements caused by the mucous membrane of the mouth, tongue, lips and other parts of the mouth, tongue, lips and other parts of the mucous membrane with a round or oval ulcers, the surface of the white color, the pain is obvious to the touch, you can use watermelon cream containing tablets or sprays, cidium iodine and so on. 2. Thrush: also known as acute pseudomembranous Candida stomatitis, is infected with Candida caused by oral mucosal diseases, can appear in the lips, palate and other parts of the mouth, do not force to tear off the white membrane, drugs have sodium bicarbonate solution, mycophenolic, ice boron powder. It is recommended to develop good oral hygiene habits, avoid spicy stimulating food, need to use drugs under the guidance of a doctor to avoid adverse consequences.