If you are using medium to high nic in 100% PG you could get a sore numb tongue, sore throat or even sore lungs. I got the sore numb tongue. Pick up some juice with 20% VG if you are using stuffing cartos, 20-30% for tanks and reservoir cartos, and any PG/VG ratio for a normal atomizer as long as it flows at least as fast as you vape it (VG is thick, juices with a lot of VG flow more slowly). Once I started using just with some VG in it, I stopped getting a sore numb tongue. Nicotine is a skin irritant. Even the patch warns about skin irritation. PG does very little to buffer the irritation. VG dulls flavor, TH and irritation but adds more visible vapor.