Ulcers on the skin of the penis may be caused by certain diseases, such as syphilis infection, herpes virus infection, glans penis and other causes. 1. Syphilis infection: It is a sexually transmitted disease caused by syphilis spirochete infection, which will form pimples and ulcers on the penile area, and often accompanied by secretions, which are highly infectious. 2. Herpes virus infection: If the penis is infected by herpes virus, most small blisters will be formed in the affected area, and when the blisters burst, ulcers will be formed on the epidermis of the penis. 3. Glandulitis: usually manifested in the glans area of the skin mucosa edema, erythema, if the condition is more serious, there may also be erosion, ulcers and other symptoms, the patient will be accompanied by local pain, pressure, itching sensation. It is recommended that patients seek timely medical attention, under the guidance of the doctor to clarify the cause of the disease in order to take corresponding therapeutic measures.