The glans skin redness is also known as the glans appears red, then the possible causes: first, local mechanical, physical or chemical stimulation and cause redness, such as the use of some exogenous drug coating, or the use of some irritating potion, excessive masturbation or excessive friction can lead to local redness, usually not accompanied by exudation, secretions, etc., and has nothing to do with infection; second, when there is a bacterial infection, such as the local presence of more More dirt or prepuce, local redness and swelling after the presence of bacterial infection, also accompanied by exudation, swelling, pain, erosion and other changes; third, if through some unclean sexual contact, infection with fungus, trichomonas, gonococcus, mycoplasma, chlamydia, etc., can appear local redness and swelling. The most typical feature of the patient is the redness and swelling after sexual contact, then it should be considered whether it is caused by STD, and the pathogenic test of relevant STD is needed to clarify.