Constant herpes on the mouth may be related to the human herpes virus, low immune function and fatigue. 1. Human herpes virus: If the human herpes virus is not eliminated from the body or if the body is exposed to objects with human herpes virus for a long period of time, the body will continue to be invaded by the virus, and herpes on the mouth will appear all the time. 2. Low immune function: If you have undergone tumor chemotherapy, radiotherapy or suffer from AIDS, the immune function of the body will be lowered, and it is difficult to resist viral invasion, thus causing herpes on the mouth. 3. Exhaustion: If you are overworked or have trauma to the skin, it may trigger herpes on the mouth. There are many reasons for herpes on the mouth, so it is recommended that the patient consult a doctor to determine the cause of the disease.