I had the same problem too the first 2-3 weeks of vaping. I am not sure if my body just adjusted to it or if i am drinking more liquid. PG/VG as others have stated is a humectant (funny this text editor/spell checker does not know how to spell humectant) which will draw moisture from you. I also vape a 30/70 or 100 vg now compared to when I started which was 70/30. Not sure if that made any difference.