When I was a kid I had a rip-roaring case of athlete's foot - both feet ha blisters between all the toes and even some on the bottoms. I remember having to soak my feet in a potassium permanganate solution several hours a day and then my mother had to wrap my feet in cheesecloth soaked with the stuff for overnight. Don't remember how many days it took, but I do remember I had orange-brown feet and ankles for about a month afterward and I ended up with a bunch of orange-brown socks as well.

That was almost 60 years ago. Hopefully there's a better cure now.

I imagine you could get it at a pharmacy or a chemical supply. Don't think there's any particular restriction on it.