Nicotine is a skin irritant
PG - thin, lets through the most flavor, most nicotine TH, most nicotine irritation
VG - thin, dulls/smooths everything PG lets through, makes thicker looking vapor
Most people use blends to get good flow, flavor and TH minus the irritation
When I started, 18mg nic in 100% PG was irritating. PG with 20-30% VG was not