Natural fibre clothing suggestions

Recommend some natural fiber exercise clothing. Especially underwear.

I've always had back/butt acne since I was a teen. It seemed to clear up a fair amount after I moved from a more humid climate to a dryer one, but in the last two years I moved back to a swampy state and it has come back with a vengeance.

I've tried a lot of different hygiene methods and laundry soaps and nothing seems to work. I recently read about someone switching to cotton underwear and it reducing their butt acne.

I'm totally down for this as I have been trying to phase out plastics from my life slowly anyway, but I'm having high school flashbacks to chafed thighs and feeling like there's a wet towel in my shorts.

If anyone has some recommendations for natural fiber exercise clothes I'd love to hear it.

I've read for some people switching to cotton underwear helped with this issue.