Hiking blisters are caused by friction. A single sock is more likely to stay with your shoe than with your foot. This leaves the sock moving against your skin, which causes friction. With two socks, especially a thin inner wicking liner and a thick outer hiking sock, the outer sock moves against the inner sock instead of against your foot and less friction is created.
Less friction = fewer blisters
Wearing cotton socks can make blister formation much worse in comparison to wool or synthetic socks, because cotton socks absorb sweat. Head over to our recommended gear page to get the best socks for this season.