Actually this happened to me when I started losing too! I even started a thread about it. I don't normally get pimples, at all. When i started losing, within the first few weeks, they started popping up!
I still haven't figured it out but after those first ones went away, I haven't had another pimple since. Friends have said that it's "toxins leaving your body" but I'm not so convinced about that.
Anyway, you're not alone but I'm all clear now so just wait it out and see what happens