I follow the Paleolithic diet and, although I haven't acne I've read that this diet is good for it. Loren Cordain claims that modern hunters-gatherers tribes are acne free as found in research and advocates this diet as cure for it. I don't know if it works but I do think it's worth a try.
http://www.ncbi.nlm.nih.gov/pubmed/1...?dopt=Abstract http://www.thepaleodiet.com/aboutus/