Mouth often long mouth ulcers specific cause is not clear, may be related to genetics, lack of vitamins, trauma, immune deficiency and other factors, it is recommended to go to the hospital for specific examination and treatment. 1. Mouth ulcers have genetic factors, the elders of the family often long ulcers, they are prone to long ulcers. 2. The most common reason for mouth ulcers is the lack of vitamins, mainly the lack of vitamin B, vitamin C and so on. 3. Sharp teeth in the mouth, stumps or eating large pieces of hard food may scrape the oral mucosa, easy to mouth ulcers. 4. The body immunity is low, there are systemic diseases may be easy to long ulcers, common diabetes, gastrointestinal diseases. It is recommended that frequent mouth ulcers should be examined and treated in a hospital in a timely manner.