The redness of the man’s urethra may be caused by overstimulation, infectious factors, allergic factors and so on. 1. excessive stimulation: men frequent masturbation or excessive sex, excessive stimulation of the urethra, may cause urethral urethral redness, usually there are no other obvious clinical symptoms, should be reasonable rest, reduce the stimulation, usually can be improved on their own. 2. Infectious factors: such as urethritis or glans penis, due to frequent stimulation of inflammatory substances on the urethral opening area, can lead to redness of the urethral opening, accompanied by glans itching, pain, frequent urination, urinary urgency, painful urination and other symptoms. 3. Allergic factors: such as the use of some of the more irritating toiletries, resulting in an allergic reaction to the urethral opening, will also make the urethral opening red, accompanied by intense itching, there will also be a local red pimples. The redness of the urethra of men, and accompanied by other obvious abnormal symptoms, should be vigilant for disease factors, it is recommended to consult a doctor for examination and treatment.