I was looking for something to explain PG reactions and the tinnitus I've developed which is getting worse. It appears to be a common side effect. Along with a few others. Very well written and explained. Read this: PG Sensitivity Introduction Throat irritation in new e-cigarette users Sensitivity to PG Sensitivity to glycerine PEG PG and VG safety issues Glycols and glycerol are alcohols Glycerine viscosity issues BTW, Due to PG issues in 1938, the FDA was formed.