That's what washing machines are for. Man, I have hats 30+ years old I probably haven't worn in over 25 years. I just like them still, but don't routinely wear a hat anyway. It's hard to sell a used hat it seems. Might as well toss out the window. See a used cap for sale at a flea market, "I ain't puttin' that on my head. Who knows where that's been?". Find one along the road and," Hey alright, a hat! Fits, too!!"