My understanding is a PG reaction is itchy skin of the minor side up to throat swelling on the serious side. A VG reaction (which is what I get) is tongue swelling and taste-buds dying. It can be really annoying, and even dangerous. Bottom line, know what you are vaping. Any reputable e-juice company should tell you which base they are using, or ratio if it's a mix. If they won't tell you, their juice isn't worth it, go somewhere else.
So, it could be a reaction to one of the bases, or just your body getting used to vaping. Vaping can be very dehydrating when you aren't used to it. So drink plenty of water and test a few different juices with different bases. If you find that there are certain juices you can't vape, don't worry, there are quite a few of us in the same boat.