sperm producing cells in the testicles are very heat sensitive which is why a human male's testicles are in the bottom of the scrotum. when cold they pull in tight. when hot they relax and pull away. the thin wrinkled skin of the scrotum also allows for rapid heat dissipation like radiator fins on a car or air conditioning unit. the type of underwear you wear makes no difference in many studies. hot tubs are indeed bad for fertility but only for the few months after until you can make new sperm (the sperm production cycle is 74 to 90 days long). i tell my fertility and vasectomy reversal patients to avoid hot tubs hot baths jacuzzis or hot saunas.
will hot baths permanently damage sperm?