About 8 years ago, I began taking pure niacin for anxiety. I followed the protocol of Dr. Andrew Saul who was taught by Abram Hoffer. I started with 25mg 3x a day and slowly worked my way up to eventually 6500mg per day in divided doses. If you watch the documentary Food Matters, Dr. Saul discusses a woman with severe depression who benefits greatly from 13,000mg per day.
Anyway, as I was increasing my dose, I discovered that my cystic acne was going away. Up til then I had horribly painful deep cysts that would persist longer than regular acne. I also noticed that the cysts I had once developed on my upper thighs and even sometimes my armpits were COMPLETELY gone. I have not had them since. And like I said, that was 8 years ago when I started.
Now, PLEASE do your research about niacin first. While I have never had any issues with it (aside from accidentally taking time release niacin which raised my liver enzymes and caused my ankles to swell - very scary. Once I stopped it, all went back to normal), it does cause a flush. This flush can be anywhere from a slight warmth to feeling like a bad sunburn. It can take 15 minutes to an hour to pass. That is why I started at a VERY low dose and very gradually worked up.
I took the 25mg 3x a day and increased by 25mg per dose every 2-3weeks. I only started flushing when I started taking 50-100mg each dose. I believe it detours the liver and that may have something to do with it getting rid of the acne. I RARELY even have a pimple now when prior to starting it, I had a horrible pizza face with redness and discoloration from the scarring.
My scarring is 95% gone too. I'm sorry for the long post but felt this was a good one to share. Again, I ONLY use pure niacin (flush niacin), not niacinamide and definitely not time release niacin. Those two are dangerous to the liver from what I've read.