they are both versons of tinea. which is a fungus.
you can take care of it with extra strength neem soap,scrubby gloves, washing everything you wear or come in contact with (like sheets) in very hot water.
topically swab area with "clean and clear" or "sea breeze" that has the strongest amount of sal. acid in it a couple times a day. the ing sal. acid is used to treat acne. it leaves behind medication that kills the fungus even when you are not showering
gold bond extra strength powder will also treat it.
avoid lotions and thing that make your skin oily.the oily skin gives it an enviroment to grow on. you cant do much about humidity which also plays a factor in the problem.