i've heard that it's from milk. whether breast milk, or (especially) formula!!! something about the hormones, and the milk, i'm not EXACTLY sure what the reason. all i know is so many of my friends kids had this, somewhat bad, and my daughter only got a few pimples a couple of times (no more then 1-5 at a time, for a couple of weeks) i noticed that when i fed her she wouldn't get them, but when she was mostly being fed by others (everyone LOVES to feed babies!) she would get them. the ONLY difference that i could tell between them feeding her, and me feeding her was that i wouldn't let ANY of the milk (neither breast, not formula since i was doing BOTH) stay on her face! i would constantly wipe her face with a warm wash cloth. once i started noticing the pimples and explained to everyone that they had to make sure they kept her face clean...she NEVER got them again!!! i mentioned this to another friend of mine and once she started wiping her son's face with a warm washcloth (sometimes a wipe) every time he'd get milk on his face, the pimples completely stopped! i NEVER put anything on her face other then the wipe or warm washcloth. now that she's 16 months old, i JUST started using some lotion, but just to keep her smooth and soft, nothing else. so i would say just keep him clean, make sure you don't let the milk just sit there for more then the feeding and immediately use a warm washcloth (or wipe if your out and can't get a warm washcloth) and it should definitely clear up VERY SOON!