Small ulcers in the mouth occur in almost everyone and are mostly caused by trauma. If an oral ulcer does not heal after 3 weeks, the cause must be identified. About 20% of the population suffers from common recurrent oral ulcers that are round or oval in shape with clear boundaries. 80% of patients have ulcers less than 5 mm in diameter that take 7 to 14 days to heal, while larger ulcers are rare and take weeks or months to heal and leave a scar. In addition, there are classified as herpetic ulcers, which take 1 month to heal. The etiology of oral ulcers is unknown, and some patients develop them for reasons related to stress, trauma, smoking cessation, menstruation, and food allergies. There is no special examination method, and the diagnosis can only rely on typical symptoms and disease history. However, the differential diagnosis should never be neglected because of this. In addition to iron, folic acid, and VitB12 deficiency, the presence of immune disorders such as chronic inflammatory bowel disease, HIV infection, and neutropenia should be considered. In addition, systemic diseases such as leukemia, lupus erythematosus, Behcet’s disease (see figure) and skin diseases should be excluded. Anticancer drugs and antithyroid drugs may also produce oral ulcers. Solitary chronic ulcers should be suspected of oral cancer. Oral ulcers may also appear as concomitant symptoms in pediatric periodic fever, pharyngitis, hand, foot, and mouth disease, and infectious mononucleosis. Treatment of oral ulcers can be done with chlorhexidine or oral hydrocortisone sugar-coated tablets, and de-inflammatory pine ointment applied four times a day, and systemic corticosteroids should be considered if symptoms do not improve. There are three types of mouth ulcers The recurrence of mouth ulcers is medically known as “recurrent mouth ulcers”. The length of recurrence is closely related to the length of history of oral ulcer, when the history is short, it can develop once a few months or a year; when the history is long, it can develop once a month, or the old and new lesions of oral ulcer alternate. In general, it can heal itself in about 10 days without leaving scars. Recurrent oral ulcers, the most common of the oral mucosal diseases, are recurrent but self-limiting and manifest locally as isolated, round or oval ulcers. There are three clinical types: recurrent mild oral ulcers, recurrent stomatitis oral ulcers, and recurrent necrotizing peri-mucosal glandular inflammation. Vitamins can treat mouth ulcers Whether the mouth ulcer is solitary or chronic, vitamins B2, B6 and other vitamin B complexes are effective. Some people even take B-complex only after one night, the mouth ulcers disappeared cleanly. When vitamin B2 is insufficient, it can trigger corns of the mouth, congestion of the eyes and anal ulcers, especially symptoms on the skin and mucous membranes. Vitamin B6 is related to the metabolism of fats, and B6 deficiency can cause lipodermatitis. Also vitamin B complex (except B1) such as pantothenic acid and biotin are both helpful in the prevention and treatment of mouth ulcers under the influence of each other.