Men with blood in their underwear are mainly considered to be related to trauma, urinary tract infections, urethral stones, genital inflammation, anal diseases and local skin breakage. 1. Trauma: such as sports, sex or masturbation, excessive force caused by the prepuce tie tear or urethra injury, etc. will easily cause local hemorrhage, blood in the underpants, mostly accompanied by pain. 2. Urinary tract infection: male urinary tract infection urethral mucosal swelling, congestion, oozing blood drops to the underpants can cause blood in the underpants, can also be accompanied by urinary urgency, urinary frequency, urinary pain and other uncomfortable symptoms. 3. Urethral stones: urethral stones embedded, can cause hematuria may cause men’s underwear with blood, can also be accompanied by renal colic and other symptoms. 4. genital inflammation: such as prostatitis, seminal vesiculitis, etc. caused by blood sperm, this time if the active ejaculation or spermatorrhea after not timely clean up can make the panties with blood. 5. Anal diseases: blood on the back side of the panties can also be considered hemorrhoids, anal fissure, anal fistula and other causes. 6. Local skin breakage: such as allergic dermatitis, eczema, glans, etc. caused by pubic skin itching, scratching caused by localized rupture bleeding on the underpants. It is recommended that men with blood in their underwear go to the hospital in a timely manner, combined with other symptoms to identify the cause of the bleeding, and actively treat it to avoid delaying the condition.