The causes of a sudden growth on the epidermis of the penis with pus include sebaceous cysts, folliculitis, prepuce and glans penis, sexually transmitted diseases and so on. 1. Sebaceous cysts: When the sebaceous gland openings in the epidermis of the penis are blocked, the discharge of secretions can be obstructed, thus accumulating here and forming sebaceous cysts. When a sebaceous cyst becomes infected, it can lead to the sudden growth of pus on the epidermis of the penis. 2. Folliculitis: when not paying attention to local skin hygiene, can lead to local skin sebaceous gland infection, which promotes the formation of folliculitis, so that the local red, swollen, painful phenomenon. It can lead to the occurrence of a sudden growth of pus on the epidermis of the penis. 3. circumcision: such as long prepuce, prepuce or urinary scale stimulation and other reasons, can lead to the occurrence of circumcision glans, so that the penile skin pimples, if this time by the bacterial infection, can lead to the penile epidermis suddenly grow a thing also pus phenomenon. 4. Sexually transmitted diseases: such as genital herpes, gonococcal urethritis, condyloma acuminatum and other diseases, usually caused by unclean sex. The above surfaces can also appear. Penile epidermis suddenly grew a thing on the surface of the situation also pus appeared, it is recommended to go to the hospital in time, active treatment.