Whoa.
First, do you have other existing allergies? Do you see an Allergist? Taking daily antihistamines is a non-issue. Especially if you may have other reasons (allergies) that you aren't even all that aware of. I have an allergic reaction to one of my freakin' cardiac medications. You know what the symptoms are? - hives and itching. The solution isn't to stop taking the cardiac medication. The solution is to take loratadine religiously. But before you write off any potential solutions you need to figure out what you are dealing with.
You have three potential sources of allergic reaction here: PG, VG (unlikely), or your flavorings or sweeteners. People here tend to fall into two very broad classes when it comes to PG allergic reaction: People like me who can tolerate PG used as a carrier in flavorings - up to about 20% of the total amount of a liquid. Or the severely allergic who have extreme reaction to any PG in a liquid. Period.
If you're actually breaking out in hives don't mess with this. Start with 100 VG at your regular nic level, unflavored, and see how that goes. If you have no reaction within 48 hours (admittedly arbitrary figure) then start introducing things back into the mix. Start adding PG only - no flavorings - to see if PG itself begins to trigger reactions again and at what level. No reactions? Then you have to start systematically looking at your flavorings.
There is no mystery to PG allergy. It's been known in the medical community since long before vaping came around. Mind you, it's still the exception - but that doesn't mean it's any less valid either. Ask an Allergist about it and see how familiar they are with the problem. It won't be a rare thing requiring deep research.
Going to try the unflavored 100% VG first. That's probably the smartest approach to it.
I'm 100% sure it's from vaping. I've been getting minor itches here and there when I started vaping, but thought it was maybe soap or my socks. I've changed to non-fragrance detergent, high quality soaps, basically everything. Can't believe I didn't think of e-liquid for so long. Anyways, it got much worse once I started getting into rebuildable atomizers and sub ohming. I vape 3x more juice and inhale large amounts of vapor... that's when it all started.
Google allergic reactions to vaping and you'll find several threads on it. I was unaware of this the entire time and hopefully these kind of things will be labeled on e-liquid bottles from now on. I'm sort of lucky because it's just rashes... other people have had their throats swollen/unable to breath.
I promise to update this thread as I go through my process so others can find a solution faster.