90% of people are sick. If one of their parents has this disease, about 50-60% of their children will get sick. Other factors: lack of trace elements such as zinc, iron, folic acid and vitamin B 12 can reduce immune function and increase the possibility of recurrent oral ulcer. Oral ulcers are mostly accompanied by vitamin B2 deficiency, and it is effective to treat them with vitamin B groups such as vitamins B2 and B6. All kinds of fresh fruits and vegetables are rich in vitamins and minerals. You can eat more yellow and dark green fruits and vegetables, and eat at least 500 grams of fruits and vegetables every day to supplement the vitamin deficiency. In addition, vitamin A and zinc should be supplemented by eating foods such as milk, eggs and wheat germ.