Joe, a 17 year old, is brought to your office by his mom. He…

Joe, a 17 year old, is brought to your office by his mom. He tells you that he has had an itchy rash on his feet for some time, but recently it has started to crack and bleed between his toes and it hurts. He takes off his basketball shoes, you note that he is wearing sweat soaked socks. You find significant erythema and diffuse desquamation between the toes on both feet. In fact, it looks like raw meat. The most likely cause of his symptoms is: