The cause of mouth ulcers is still unclear, and is considered to be related to genetics, immune factors, mental factors, viral infections, dietary factors and other reasons. 1. Heredity: patients with mouth ulcers are mostly considered to be genetically related, and some studies have shown that mouth ulcers have a genetic predisposition. 2. Immune factors: if the body immunity is reduced, the body may lead to pathogen attack, which is also easy to lead to mouth ulcers. 3. Mental factors: If the patient has long time mental stress or life stress, and often emotional disorders, it may also lead to mouth ulcers. 4. Viral infection: mouth ulcers can be caused by viral infection, herpes pharyngitis can be manifested as star-shaped mouth ulcers, a large number of systemic symptoms. 5. Dietary factors: for long-term partial eclipse of the population, if the nutritional intake is not comprehensive, the body lacks vitamins or iron and other minerals, can also make mouth full of mouth ulcers. It is recommended that patients with mouth ulcers need to consult a doctor in a timely manner, the doctor will choose the appropriate measures for the patient’s condition. Mouth ulcers may be associated with systemic diseases, so it is necessary to go to the hospital for timely examination.