How to avoid rashes on the top of my feet?

I love wearing my Toms and Sperry's without wearing socks, but I have noticed that after a few weeks I get a rash on the top of my foot from wearing the shoes without socks. The rash goes away after I treat it with anti-fungal stuff, but I want to know how to prevent this from happening again. Will washing my shoes in the washer get rid of the sweat and fungus that most likely causes the rash or am I stuck wearing socks with my shoes?