Suggest Remedy For Rashes On The Body

MY BOYFRIEND HAS A RASH BEHIND HIS NECK ON HIS UPPER BACK ..LOOKED LIKE PRICKLEY HEAT.. THEN IT SPREAD TO THE CHEST AND STOMACH.. THEN IT DOES NOT ITCH OR BOTHER HIM.. AFTER A MONTH THEN I GOT A RASH BACK OF MY NECK SHOULDERS BREAST LOWER MID BACK AND NOW SIDES OF MY STOMACH. IT DRY AND LOOKS LIKE WHEN YOU HAVE THE CHILLS YOU GET GOOSE BUMPS... SOME AREAS IT WELL GO AWAY UNLESS COLD OR RUMB THAT AREA I DONT KNOW WHAT IT IS.. I AM GUESS BACTERIA RASH OR SOMETHING I GUESS IN AREA WHERE YOU SWEAT.. CAN YOU PLEASE HELP ME ITS ON MY ARMS ALSO UPPER WHERE SHOULDER IS I TRIED POWDERS AND LOTIONS