Mouth ulcers are a common ulcer-like disease that occurs in the oral mucosa, most commonly found on the inner lips, tongue, tongue belly, buccal mucosa and other parts of the mouth. Causes of oral ulcers include heredity, local trauma, mental stress, low immune function, etc., as explained below: 1. Mouth ulcers have an obvious relationship with heredity, and according to epidemiologic surveys, a portion of patients have a family history. 2. Low immune function makes the body susceptible to pathogen attack, resulting in mouth ulcers. 3. Mental tension, stress, anxiety, etc. will affect the normal metabolism of the human body, most of the patients with reduced sleep quality, the rhythm of life and living habits have a certain relationship with the occurrence of oral ulcers. 4. Poor dietary habits such as picky eating and partiality can lead to oral ulcers caused by the lack of iron, zinc, folic acid and other important trace elements. 5. Physical injury leads to oral mucous membrane damage caused by mouth ulcers. For example, trauma, burns, etc.