I found that putting foundation on whatever acne you have (back, face, chest) it dries them up, and they tend to go away in a few days. It has worked a charm on me for years. Of course you cannot use oily foundations. (Avoid l'oreal as it's more oily, along with brands that are not well known)
I use it from the company maybelline, it takes a few days but as the days go by you can notice that they are going down. It generally starts to make it dry (example like scabs, but not hideous ones) then it fades away.
It's worth a shot, also be sure to drink lots of water! If you are drinking any sugary drinks (pop, fruit juices) they contribute to the problem.