I wash everything before wearing, no matter where it came from. I used to work with a girl who got a fungal infection on her skin (across her shoulders and upper back, up the back of her neck, and into her hair) from time to time, and it was very hard for her to get rid of. She had medication for it, but also had to simultaneously wash every article of clothing she owned and every piece of bedding in very hot water in order to clear up the rash---sometimes more than once during the length of time she was on medication, since she could reinfect herself with the fungus by putting on her own clothes. That means she may have gotten the initial infection from clothes tried on for size in a store, which means you can get that infection by trying on clothes in the store which were previously tried on by another shopper with the rash. Imagine having to wash every piece of clothing you own and every piece of bedding. It was awful for her, and this rash recurred on her several times during the years we worked together.