Most of the women in my family suffer from adult acne until menopause.. I did some research and through trial and error found a solution..at least for myself.. but maybe something to think about..
In my opinion there are 2 kinds of acne.. hormonally caused which produces deep cyst acne that takes forever to go away and "regular" surface acne (whiteheads etc) that is caused by your skins inability to slough off dead skin quickly enough. I spent YEARS trying everything from natural creams to every dermatologically prescribed nightmare. I finally started to research this idea on my own and came up with a theory that my acne was in fact caused by a higher level of progesterone This hormone is what rushes in a puberty and normally subsides as you get older. If you are an adult female and have a high level of progesterone it can cause varying degrees of hirsutism (excess facial/body hair) acne, and sometimes make the hair on your head thin.
My solution was to take this birth control pill from Europe called Diane 35. I ordered it online as it is not available in the US. It is designed specifically to balance the production of progesterone. I swear to god, it totally revolutionized my skin! I took it for about a year and now, five years later I get a little zit every once in a while but NOTHING like the horrible painful acne I had before. It also made my body hair finer..(im not really hairy to begin with but I did notice a difference)
Obviously everyone is different but adult acne, I believe, is generally hormonally based so this could be something to check into. Some people have success with estrogen based birth control pills.. but in my experience it was the progesterone that was the problem.