Recurrent oral ulcers are the most common, recurrent, and etiologically unknown of the oral mucosal diseases. Synonyms include recurrent aphthous ulcers and recurrent mouth sores. The etiology is very complex and has significant individual differences. Clinically, according to the size, depth and number of ulcers, they can be divided into recurrent light oral ulcers, recurrent stomatitis ulcers and recurrent necrotizing mucosal glandular periarthritis. The treatment principle is to eliminate the causative factors, improve the health of the body, reduce the local symptoms and promote the healing of ulcers. Although there are many clinical treatment methods and drugs used, there are no specific drugs available. The systemic treatment is generally supportive and immunotherapy is adjusted. The principles of treatment for RAU should include two main aspects: 1. Local drug treatment. The main purpose is to prevent secondary infection, reduce pain, and promote healing in order to shorten the course of treatment. The drug dosage form is solution or bulk. Commonly used 5% dacronin local application to play a pain-relieving effect, with compound boric acid solution and 5% chlorhexidine gargle, lysozyme tablets, anti-inflammatory film and a variety of Chinese medicine bulk can play anti-inflammatory antiseptic effect. 2. Systemic treatment. The main purpose is to prevent recurrence, which can be treated with immunosuppressive drugs and drugs that improve the function of the immune system. (1) Immunosuppressive drugs: such as glucocorticosteroids, commonly used prednisone 15-40 mg daily in 3 doses. For medium and long courses of treatment, alternate day therapy can be used, that is, the total dose of two days combined in the morning in one dose, which can reduce the side effects and its impact on metabolism. In addition, cytotoxic drugs have non-specific anti-inflammatory effects and are often used clinically in combination with glucocorticosteroids. Azathioprine is more commonly used at 20-50 mg twice daily for 1-2 weeks. Cytotoxic drugs are highly toxic to proliferating lymphocytes, but not to differentiated and mature plasma cell type sensitized small lymphocytes, therefore, they should be discontinued when the course of treatment is not obvious or the disease turns dramatic. Other drugs include alkylating agents, cyclophosphamide, etc. In the application of immunosuppressive drugs, the patient’s systemic condition must be fully understood before administration, and blood and liver and kidney functions should be checked regularly during the course of drug administration. (2) Drugs to improve immune function: such as transfer factor, levamisole, gammaglobulin, etc.