Mouth sores at the corners of the mouth may be related to trauma, genetic factors, immune factors and other causes. 1. Trauma: If the mucous membrane at the corner of the mouth is damaged when eating bones or fish spines, it may cause mouth sores. 2. Genetic factors: Recurrent mouth sores are related to heredity, and if parents have recurrent mouth sores, their children may also have them. Common triggers include stress and anxiety, hormonal changes and so on. 3. Immune factors: Decreased immunity makes the body susceptible to pathogens, leading to the occurrence of mouth ulcers. It is recommended that people with mouth sores go to a regular hospital in a timely manner to clarify the cause of the disease and standardize the treatment under the guidance of the doctor, so as not to delay the disease to bring adverse consequences to the body.