"I did have a few red bumps appear after a few weeks, but these dissappeared very quickly, and were not what I would call pimples, merely raised lumps with no pus or head."
This is precisely what I have too, there's no head. They are located in the classic spots in my face where occasional pimples arise. That's why one of the hypothetical explanations I gave to myself is that it's actually Iodine healing those spots. Could it be, according to your experience?