Acne

I'd like to add one question to the "Contribution"-list earlier. How does acne appear? Does it fly around thinking "yeah, there's a body I'd like to invade" or how does it work? I still occasionally get the odd acne-spot despite being "middle-aged" (preferably when I've been eating chocolate...and everybody knows chocolate is pro-acne, but WHY?). I didn't have acne problems when I was a teenager, like many others, but why do I still get it? I can understand if it wants to settle in my face (always been pretty :)...yeah, yeah, space for comments here) but in my ass?