Redness and swelling in the urinary place of a 9-year-old boy may be caused by over-irritation, infection, allergy and other factors. 1. overstimulation: for example, foreign body stimulation, resulting in damage to the urethral area, may make the urethral area red, swollen, may also be accompanied by significant pain. 2. Infection: for example, urethritis or glans, may be related to poor hygiene, by inflammatory stimulation, may lead to urethral area redness, swelling, may also be accompanied by glans itching, urinary frequency, urgency, urinary pain and other symptoms. 3. Allergy: for example, the quality of underwear is poor, and frequent contact with the urethra, causing an allergic reaction, which may lead to redness and swelling of the urethral area, accompanied by intense itching. Redness and swelling in the place of urination of a 9-year-old boy indicates the presence of abnormalities, and parents are advised to take their children to the doctor for examination and treatment in time.