The main reasons for white patches on the inside of the lips are: 1. Suffering from mucosal leukoplakia or lichen planus. Like drinking, eating too hot or sour and spicy food, having the habit of chewing betel nut, etc. will cause stimulation to the oral mucosa and lead to mucosal lesions. The lack of trace elements, especially fat-soluble vitamins, is also the main cause of leukoplakia.2. Ectopic sebaceous glands, ectopic sebaceous glands on the buccal mucosa belong to the normal range, mainly manifested as small pinhead-shaped yellowish patches, which can fuse into patches or irregular yellowish-white patches, and the performance is more obvious with the increase of age. For oral leukoplakia or lichen planus, prompt medical treatment is required, especially for leukoplakia because it is a precancerous lesion and requires increased vigilance. White edema of the mucosa and ectopic sebaceous glands can be observed regularly without special treatment.