According to a new study, you should throw away your underwear every YEAR . . . or it becomes a health risk.
Even though you're washing them after you wear them . . . hopefully . . . old underwear can still develop a buildup of bacteria like E. coli. That can lead to you getting infections down there. And NO ONE wants those infections.
Of course, not everyone is even washing them regularly. The study found 18% of men and 10.5% of women wear underwear multiple times without washing them.
And one more thing: The researchers also say you probably shouldn't wear underwear when you SLEEP . . . nude is better.