Just in case you needed a government agency to confirm something completely obvious for you: no, an iPhone app that claims to cure acne will do no such thing.
It's kind of ridiculous that the FTC had to say anything about this at all, but I guess that's the world we live in. The apps in question claim that light therapy using different colored lights from the phones screen can help reduce acne-causing bacteria. Never wash your face again!
Obviously (or so one would think), that is a steaming pile of acne-covered BS. Even the FTC says so, which should end the lives of these scammy apps pretty quickly.