Was just the opposite with me, PG was causing major sore throat, lung pain, coughing....felt like I was breathing fire. After switching to 100% VG problem went away, and have been fine ever since.
However, cold sores are not caused from dryness, they're cause by a virus in your body which are triggered by changes in normal body immunity. Any changes in stress, diet, increased or over-done vaping, winter-summer conditions can cause excessive dryness, is a very good thing to do normal maintenance like increasing water, eating and drinking more vitamin-C, all the B's and D, and increasing fiber can be beneficial to maintaining hydration, from within! Use of high-antioxidents can also be helpful.
Sometimes even a change in toothpaste can bring on mouth upsets, changing the PH of tissues. Both PG and VG are also anti-bacterial, so can cause a little change in tissue hydration. Some flavorings in the juice you use can also cause reactions due to PH changes, if you skip around experimenting with different ones you may want to take notice of how they affect you short- and long-term and desist with using the ones that can irritate vulnerable throat mouth and nasal tissues. I really am doubtful a 10% change in PG or VG could be so drastic, but everyone is different physiologically.
Facial dryness is helped with hydrating cleansers, skin creams.
For me that's a normal thing even before I started vaping.
None of us drink enough plain old water!
