violetgrace
neem soap is the best thing for that.
use it just like you would a bar of soap
then right after the shower sprinkle some gold bond extra strength powder on it.
wear boxers that are made of cotton.
this is the one i used to get rid of a tinea i had (like jock itch but on your torso and neck)
http://www.bytheplanet.com/MoreInfo/details.htm?prod=1000OR&PropPass=neem
everything else i tried didnt work.
you might want to cut the bar in half and use it on your face. its an amazing face soap too.
you do have to adjust your diet as suggested above as well. or it will come back after you stop using whatever method you do to treat it.
more on neem:
http://www.bytheplanet.com/WhatAilsYou/JockItch/jockitch.htm
i havent tried the oil,powder or lotion. but that bar soap worked well.