I have a sensitivity to PG but not an allergy. At about 2 mo. into vapeing I started to get crazy itching that would move from one spot to another. I found it was PG but also noticed it was the amount of PG. I am one of the lucky ones and can still use PG based flavors and the rest just plain VG, I mix my eliquid at 20-24% PG based flavor and the itching has stopped. Unless a flavor says different I would assume it to be PG based, as most are. There is a new super concentrated flavoring that I know e-cig express carries (and probably somewhere in the UK as well) that only use 2-5% flavor that I believe is an alcohol based flavor.
http://www.ecigexpress.com/flavorsexpress-fruitexpress-c-16_96_97
http://www.ecigexpress.com/flavorsexpress-fruitexpress-c-16_96_97