tinea versicol
"I use a prescription for selenium sulfide 2.5.  I've tried using it in different ways over the years, but the way that works for me is to slather it on with a little moisture before bed, sleep in it and then wash it off in the morning.  Doing this for 3 consecutive if uncomfortable nights rids me of it for about a year.  I can't get that sulfur smell out of anything I wear though, so I find some old clothes that I can throw away after the third night."