First off, let me just give you a quick tip about these forums. Experts check in about once a week, though a few check more often than that, so you probably won't get a response to your question for about 24-48 hours unless someone just happens to be online. Don't expect answers "ASAP;" this ins't a live forum.
To answer your question, I would type the words "chocolate" and "acne" into a search engine like Google. I would be careful in looking at particular sites; some are MUCH more reliable than others. Look for URLs ending in .edu, .org or .gov instead of .com.
A quick peek at the Google results revealed this site, which is both reputable and full of good information:
http://www.nlm.nih.gov/medlineplus/acne.html. Also take a look at the information on the website of the American Academy of Dermatology; a link to the site is in the site I provided.
