I've been using it for a while do deodorise my shoes. It seems to be effective at killing whatever makes them smell. Anecdotally it also works for killing fungal infections of the feet too, although I've switched to using iodine, which is actually proven to be effective and tends to clear fungal infections within a couple of days.
I had a spray can of 100% tea tree oil that I would spray on my feet. It would sting like hell anywhere I had broken skin but it was effective.
Iodine is much more pleasant to use and doesn't smell so bad, it's cheaper too.
I'm sure there is a more exact specification, but it all seems to work. Problem gone in a day or so.
Get some bleach, mix in a basin with some water. No good exact amounts, it should smell bleachy and be diluted a fair bit past the point of burning.
Do this, then a couple days later, do it again. Whatever has taken residence on your feet will have moved out.
You just apply it topically and it will kill any fungal infection within a couple of days.