A red pimple on the epidermis of the penis, pain, may be caused by factors such as circumcision, folliculitis, condyloma acuminatum and so on. 1. circumcision: may be related to poor personal hygiene, due to the foreskin as well as the glans localized inflammation and infection, local stimulation, may lead to penile epidermis red bumps, accompanied by pain, itching and other symptoms. 2. Folliculitis: not paying attention to the penile area care, resulting in local hair follicle infection, induced folliculitis, may appear red bumps, accompanied by pain, swelling and other symptoms. 3. Condyloma acuminatum: the presence of unclean sex in men may lead to human papilloma virus infection, so that the penis localized condyloma acuminatum, may appear skin color or red bumps, accompanied by mild itching as well as pain. A red bump on the epidermis of the penis, pain, should be alert for the above diseases, it is recommended to consult a doctor for examination and treatment, do not self-medication, so as not to cause danger and delay the condition.