I don't remember if I actually believed this or not, but my grandmother used to tell me that virgins weren't supposed to use tampons.
A childhood belief about periods

others believed things like this
- I used to think the word "european" had something to do with pee, and that kids weren't supposed to say it.Anon
- I once was told that ONLY virgins get acne. After sex, no new pimples grow. I believed that.— MD Caruso
- I used to believe that virgins can't have sex and have to wait till they're not.— [to_xp]Gekko
- I used to believe that virgins were an organized reliougous group who chose not to have sex.— Pamela
- My Grandmother once told me she could unscrew her feet. I believed that for years.— Andy Bettison
- that u unrolled tampons and placed them in ur underwaer— DKuser