PG and VG are both humectant/dessicants
A desiccant or humectant is a hygroscopic substance that induces or sustains a state of dryness (desiccation) in its local vicinity...
When you first start vaping your body is not one bit used to this, and you'll notice it a LOT. As you vape more you get accustomed to it. I personally think it's because you start drinking more water to accommodate, and it just becomes second nature.
Keep yourself hydrated, and carry some gum to keep saliva flowing. I find it's the worst when I first wake up, and now always go to sleep with a glass of water beside the bed.
Anyway, it's perfectly normal.
Another side effect I experienced was a tight/soreness in the larger muscle groups, particularly upper legs. This passes after a couple weeks also.
propylene glycol is eliminated from the body by oxidation through alcohol dehydrogenase to form lactic acid
Normally (via exercise) this build up occurs and the body rids itself of the excess after an hour-ish. When vaping you are supplying a continuous supply.
After such exercise, the muscle adapts rapidly to prevent muscle damage, and thereby soreness, if the exercise is repeated
Hope this helps.