I get the same thing happening alot considering I'm a carless girl living in South Australia.... lots of walking and lots of heat...makes the legs verily sore

But enough of my complaining... the best way I've found to cure it was actually advice from my mum... you use the anti nappy rash baby powder (the one I use is called Curash, but idk if you can buy it outside Aus) because it's formulated to cure basically the same thing - a rash due to rubbing and sweat

Hope it helps!