The skin of the penis is red, there may be inflammation, trauma, venereal disease, malignant lesions and several other causes: 1, acute inflammation of the penis: such as circumcision, glansitis and other conditions, mostly seen in patients with long foreskin or prepuce, because the foreskin is too long wrapped spare the glans, weak or erect situation, the glans can not be normally revealed, if, daily personal hygiene cleaning is not timely, easy to form foreskin scale, repeatedly stimulate The glans, resulting in local inflammation, redness and pain of the glans and foreskin, may be found some small herpes, may be accompanied by local itching, need to pay attention to personal hygiene, if necessary, can go to the public hospital urology examination to see, may need to do circumcision. 2, penile trauma: most often seen after violent masturbation, repeatedly rubbing the penis, will lead to local redness and pain of the penis, you need to quit masturbation habits, local symptoms can slowly recover, in addition, if the underwear is tight, daily penile squeeze stimulation, will also lead to penile redness and swelling, you can consider replacing the cotton underwear, appropriate loose some, can also reduce the local squeeze stimulation. 3, venereal disease: If you have unclean sex before, you may be infected with venereal disease, such as gonococcal infection or non-gonococcal infection, etc., can also be manifested as local redness and swelling, and may be accompanied by urethral discharge, you need to promptly seek medical examination, do the culture of secretions and laboratory tests to clarify the type of infection, and timely treatment. 4, malignant lesions, malignant tumors of the genitalia are relatively rare, if the penis appears red and swollen, while appearing cauliflower-like things, we should consider whether there is a case of malignant lesions, it is recommended to seek medical examination in a timely manner. In short, if the skin of the penis appears red, it is best to find the cause, if it is pathological factors, or the need for timely treatment to avoid aggravation of the condition and delay in treatment.