The Help actress hit rock bottom after suffering severe break-outs as a teenager, and she was put on prescription medication to combat her spots.
Stone's pimples returned as she struggled to shoot her first lead role in Easy A, but she admits her skin was made to look flawless in the 2010 comedy.
She tells fashion and beauty website Refinery 29, ""I'm actually pretty interested in skin care, because I had bad hormonal acne when I was 17, and they put me on Accutane (acne medication) for it.
""After two months on the Accutane, I went off of it, and since then, my skin, my mouth, my lips, my eyes are all so dry. Then, I had stress acne when I was 20, when I did Easy A, which they kindly video-airbrushed out of the movie.
""But I realised how debilitating and embarrassing it can be to have cystic acne. So, I'm really interested in the biology of what makes up acne and how to work on it from the outside, too.""