I agree that hormones are the cause of Acne also since I have never seen a youngster that hasn't hit puberty with acne. I also never had a zit till puberty and have had them forever since even if it is only the blackheads which don't show that much. Somehow hormones cause bacterial growth in some people that results in zits. Maybe Iodine causes a increase in the release of the bacteria in the early stages and then controls it in later stages before it can become a problem.