Oral mucosal fibrosis often occurs in people between the ages of 20 and 40, and the disease often occurs in the posterior cushion area and the buccal mucosa. Oral submucosal fibrosis (OSF) occurs worldwide, with the most patients in India and some in other parts of Asia, and there are about 2.5 million OSF patients worldwide according to statistics. The causes of oral mucosal fibrosis 1, nutritional deficiencies: In Malaysia, 77% of patients with OSF were found to have vitamin B-comples and iron deficiency. However, in Western countries, although there are above nutritional deficiencies, but there is no occurrence of OSF, so it may be because the patients with OSF have a gradual decrease in mouth opening, burning sensation when eating, not easy to swallow, and cause the situation of nutritional deficiency. 2, curry: because Indians often eat spicy food, so some scholars believe that curry may be the cause of the disease. However, in Mexico and the West American residents, they consume a similar amount of curry, or even more than the Indians, but there is no occurrence of OSF. 3, betel nut chewing: According to a 10-year study on India, there is no OSF without betel nut chewing, and among people who chew betel nut, 35 out of 100,000 people suffer from OSF every year. Betel nut alkaloids are the extracts of betel nut, which can stimulate the synthesis of collagen and increase the amount of collagen, causing OSF. 4, clove oil: clove oil is one of the main ingredients in betel nut, if the amount is higher than three millimole per liter, the amount of clove oil can cause OSF. If the amount is higher than three millimole per liter, it will cause cytotoxicity to the fibroblasts of the oral mucosa, which will increase the destruction of the tissue and finally lead to an increase in the formation of scarring. 5. Immunological aspects: Some scholars believe that autoimmunity is the cause of OSF: (1) the occurrence of OSF is more frequent in women (in India); (2) the age of occurrence; (3) the incidence of autoantibodies; (4) the infiltration of lymphocytes in the lesion; (5) the increase of human leukocyte antigen H-A10 and DR-3 in OSF patients. However, it is also possible that the chronic tissue destruction caused by OSF may lead to immune problems. Among the above-mentioned causes of OSF, betel nut chewing is the main causative factor.