Weird rash because of exercise?

[Killua]

I started going to the gym last month and I've been getting this weird rash on my legs. I'm pretty sure it's because of the exercise or the sweat thanks to google.

I actually have an appointment with a dermalogist tomorrow, but I was wondering if anyone ever got rashes because of similar causes and if there is some kind of cream you can use to avoid it?

thanks