Hmm, I wonder if an individual is doing lots of things that are promoting the production of lactic acid, and then propylene glycol on top of that, which can be converted to lactic acid, would have an effect?
In which case, vg would be the way to be, but I could be talking oot me arse.
Still, I make my own eliquids mainly, and my VG is from Boots, and is just their cough medicine without the added ingredients. And you can buy VG nic base easily. Don't think it is that easy getting vg based concentrates though, but some ranges, say Inawera, only need tiny percentages anyway.