The blackening of glans may be a normal physiological phenomenon, and it may also be caused by factors such as circumcision and glansitis, penile cancer and so on. 1. Normal physiological phenomenon: when men’s age increases, there may be pigmentation in the glans area, which will lead to darkening of the glans, usually in dark red color, with no other clinical symptoms, and no need for other treatment. 2. Circumcision and glansitis: men do not pay attention to the hygiene of lower body for a long time, which may induce circumcision and glansitis repeatedly, due to the chronic inflammation stimulation, it will also lead to the blackening of glans, which may be accompanied by itching and pain of glans and other symptoms. 3. Penile cancer: it may be related to chronic inflammation stimulation, smoking and other factors, which will lead to malignant lesions in glans area, and the aggravation of lesions will lead to black glans, accompanied by swelling, erosion and other symptoms. Darkening of glans with other abnormal manifestations may be due to the presence of disease factors, and it is recommended to consult a doctor for examination and treatment.