I have been vaping over two years and have been totally cigarette free two years next month. I have vaped both PG and VG and combinations of the two.
Over these last two years, I have had some cold sores or blemishes is more what they seem to me. Being 59, I don't get the "teenage" blemishes any longer, but I do get these from time to time, but they are not nearly as bad to me as the side effects of smoking, so I just put on a little Carmex and a little cover stick if going somewhere, just to cover it a little and they go away quickly, a couple of days.
I have started cleaning my drip tips a little more often, and wiping down the cartos I sometimes use, and it does seem to help make the blemishes a little less frequent.
I have heard from some others that they think it also could be effected by the drying of the membranes around the mouth.
What I do know for certain in my case is that they are not serious or anything that would keep me from vaping. And if I drink more water, I don't seem to get as many either.