Ulcers on both sides of the inside of the mouth may be caused by oral ulcers, oral herpes simplex, pemphigus and other conditions. 1. Mouth ulcers: the etiology of the disease is not clear, most considerations are related to genetic, dietary, immune and other factors, and women’s premenstrual serum progesterone is low, also prone to mouth ulcers. Generally common in the cheeks, lips, soft palate and other mucous membranes, the ulcer surface has a depression, and the surrounding congestion and redness, there will be obvious pain. 2. Oral herpes simplex: usually due to type I herpes simplex virus infection, and also related to fever, ultraviolet light, trauma, gastrointestinal dysfunction, pregnancy, mood changes and other factors. Patients often appear in the oral cavity clustered small blisters, followed by the oral mucosa will form vesicles or shallow ulcers, which can also be manifested as the inside of the mouth on both sides of the ulcers. 3. Pemphigus: this disease is an autoimmune disease, mainly due to the patient’s immune system disorders, and also with the use of captopril, rifampicin and other drugs. Generally common type pemphigus occurs in the oral cavity, chest, back and other parts of the body, serious cases can be generalized, and almost all patients have blisters or erosion of the oral mucosa, can also appear inside the mouth on both sides of the ulcerated situation. It is recommended that when patients have ulcers on both sides of the mouth, they should seek medical attention to clarify the cause of the disease and follow the doctor’s instructions for reasonable treatment, and the use of drugs should be in accordance with the doctor’s instructions.