Since you lowered your nic, and the problem is still there, it could be the dreaded allergy that some people have. I can only suggest this: lower your nic again or go to a higher VG percentage. If lowering it again doesn't stop it, then it is probably the PG that you're having problems with.
When I first started vaping, I couldn't do PG at all. Made me itch to death. Everyone suggested going to all VG and gradually adding PG back in (small percentages at a time) on future orders to see if the problem returned. That's what I did. I ordered all VG and the problem went away. Ordered 10/90 still no problems...and just kept going. For some reason with me, it worked. Now I can vape straight PG without any itching.
You might give it a try to see if it is indeed PG and not the nic that you are having problems with. Off the top of my head,
vaperite,
cloudsofvapor, and
freedomsmokeusa (on flavor range juices only) offer 100% VG. Bruce at COV is highly allergic to PG so even his flavorings have a different base. Vaperite is all organic as well and really tasty stuff IMO. Oh I forgot one...virginvapor is all organic. I don't know about virginvapor juices yet since I just ordered. Here is the link to her
website and
forum.