One of the really day-to-day useful uses of Boric Acid (I believe borax is also effective) is to add it in powdered form to shoes to kill any bacteria growth.

I started doing this a few years ago after watching a video from Big Clive where he mentioned it, and it has really made a difference. No more smelly shoes, socks or feet and no fungal growth.

Seems silly but living under the tropics and macerating in closed shoes all day does have these rather annoying side effects, and whatever shoes you wear, sweat and a warm environment are a breeding ground for bacteria.

Adding about half a teaspoon of powdered boric acid to each shoe at least a couple times a week makes a huge difference.

Best is in new shoes, they will smell like new even a couple of years later. I'm not even exaggerating when I say that at the end of a long day, socks only smell of fabric softener and feet smell of well, nothing.