I don't know, either. I suppose it's possible that second-hand PG exposure could lead to a rash, since just about anything can cause contact dermatitis in sensitive people. The thing is with PG, though, it's in just about
everything: toothpaste, nearly all store-boughten baked goods, lots of other prepared foods, cough medicines, underarm deodorants, just about anything you'd smear or spray on your skin or into your bodily orifices (lotions, etc.), and the list goes on and on and on. It's even in most latex paints, and it can evaporate from freshly painted wall surfaces for weeks after painting.
If someone has such extreme sensitivity to PG, I'd suspect the sensitivity would have manifested with something else containing PG by now, rather than the miniscule concentration of PG in second-hand vapor.
