Anecdotally, my over-2 decade long acne problem vanished when I was travelling through places that were sparsely populated / had little pollution. These were modern western societies and I didn’t exactly eat healthy… but the environment was clean. I didn’t wash my face with face wash then as I ran out along the way and didn’t get more. When I travelled through cities a few zits would pop up, but then go away again when I was back in less populated areas.