The crown of the glans is purple, then the possible causes: 1, long foreskin or prepuce, when there is long foreskin or prepuce, the glans is wrapped for a long time, so there will be a localized secretion of foreskin scale to stimulate and produce localized purple. Generally not accompanied by any pain, not accompanied by local secretions, without any self-awareness of the symptoms, just in the cleaning when turning the foreskin, can see the local purple and other changes. It may be related to factors such as being wrapped for a long time and localized chronic hypoxia. This situation generally do not need special treatment, need to do a good job of personal hygiene regular cleaning, can also be circumcision surgery. 2, the glans infection, this is can appear localized purple and red, accompanied by pain, accompanied by secretion. May be related to bacteria, fungi, trichomonas and other infectious factors. Acute phase can also be accompanied by erosion, exudation and other changes, need to carry out relevant etiological testing, such as the diagnosis of the existence of related infections, it is necessary to carry out topical drugs, or local cleaning and other treatments.