Miconazole Nitrate cream (2%) works well for me as a preventative. It's sold in drug stores as antifungal cream.
If you get a case of the crotch rot, Monistat 3, believe it or not, works wonders. It's just Miconazole Nitrate cream, but it's 4%. Soothes itching right away and gets rid of the stuff fast. I'm sure most of the women out there know exactly what I'm talking about. You have to be pretty secure in your masculinity to buy the stuff at the drug store if yer a guy (or *Butch*). I don't have to worry about it much, I just ask the wife to pick some up.