Suggest Remedy For Itchy Rash On Thighs

I get a rash that appears quickly (usually at night) and is gone by morning or sooner. It itches and if I scratch, the rash becomes redder in color. But by morning it's typically gone. This has been going on for over a year. The rash doesn't appear every day, but two to three times per week. It usually impacts my thighs, buttocks, stomach and arms. As I scratch, the rash pops up in other places, almost like it's moving.