I bought the whole foods brand of biotin (1000 mcg) and I've been taking it for about a week so far. I was really nervous about taking it because of all the things I'd heard about it causing acne, but as someone who has struggled with severe skin issues her entire life (I used to have really terrible cystic acne: had to go on Accutane for it), I can say that I've seen a HUGE improvement in my skin since I started on biotin. I went from having breakouts all over my face to having clear skin within days (seriously, not an exaggeration). I started taking biotin to try to help grow out my hair faster (I got a pixie cut in early September and I've been growing it out ever since). I haven't seen a huge, drastic change in terms of hair length, but I've only been taking it for a week, so we'll see what happens long-term. Even if this supplement doesn't do anything for my hair, I'll probably keep taking it because it benefits my skin so much.