DIY your juice. Swap stuff around. How do you know for sure it's the PG? (it may very well be...not saying it isn't).
I know some flavorings do that to me. Also, some VG does it. I know this because I DIY my juice. One supply of VG from a different than usual vendor did that to me. When I swapped it out, hives went away. Swapped it back in, they came back. Same nic base, same flavorings otherwise. Just a VG change. Not all VG is the same. Some comes from coconut, I think. Some doesn't.
If you DIY, you can do this type of swapping thing. Some flavorings do it too (for me). So...there's almost no way for you to know unless you've had tests or know from experience that it's PG. If it's a common flavoring or two, you won't know unless you DIY because they don't publish the recipe.
Also, when you get a juice you may have to shake it well and let it steep for a couple of weeks. It may go from horrid to wonderful.
I don't know 100%. I'm trying to figure it out. Thursday I vaped a 100%VG organic. I didn't like the taste much at all, but used it just to see if I'd have any kind of adverse reaction to it. I was fine, no itching, no hives. But the juice was just not something I could stand to vape and I have other 100VG samples that should be here on Monday.
But then yesterday - Friday - I pulled out an old bottle of PG based eliquid that I had purchased from a completely different supplier than what I had been using regularly (the 50/50 that I've been using daily for the past couple months that's been giving me issues) and vaped that most of the afternoon. By midnight last night, I had broke out in terrible hives and barely slept all night. So I have to assume a pretty good guess is that it's the PG.
I mostly wanted to put in were this: Getting the hardware 'right' is a big factor in taste and 'enjoyability.' That said, the biggest hurdle I encountered, was finding an eliquid that I could tolerate, let alone enjoy. I ordered juices that were getting the best - or the most - recommendations in ECF. But of course, taste is totally subjective: The first 6 I tried were barely tolerable, nasty even. After sampling about 20, I began to find a few I liked and a few vendors who sold juice that seemed to suit my taste. Things have gone uphill from there and I'm really enjoying vaping.