Do we know for sure what causes it yet? I'm fucking 23 and I just started getting acne again despite living a very healthy lifestyle. I was acne free for 4 years after puberty and now I look just as bad as when I was 16. I eat a healthy, vegan diet and exercise 3x a week. I'm in university and stressed but no more than I was as a freshman/sophomore/junior. What the FUCK is going on?