Hello, I have switched over to electronic cigarettes and am experiencing something I have not read about involving them. The Juice I am using is Propylene Glycol(PG) based and ever since I have been using this I have been coughing a lot as well as coughing up a clear-like mucus from my lungs. I had a cough about a week before I purchased the electronic cigarette and thought at first that it simply has not come to pass until I decided to stop using my electronic device as I began getting headaches due to coughing so violently. The symptoms ceased momentarily, or at least to the point that I now know that the electronic cigarette's vapor is the cause(PG). Am I allergic to PG? Should I switch to Vegetable Glycerin based liquids? Or is it simply that with excess vapor in the lungs I inducing coughing? Thank you for reading.