The risk of being allergic to vegetable glycerin is very low. The only patient population which may experience problems with metabolism of Glycerol would be diabetics owing to the anabolic hepatic pathway which can convert free Glycerol to glucose (but this would still not be an issue at the levels used in vaping).
The most common noted side effect of inhalation of E-Liquid containing vegetable glycerin is a dry mouth, sore throat, and increased thirst. These symptoms usually last just a few days to a week as the body gets use to the vegetable glycerin. These symptoms can be lessened by drinking more water and liquids then usual for the first few weeks of using your E-Cigarette.
If you are moving from smoking traditional cigarettes to E-Cigarettes, you will find there are many side effects of quitting smoking tobacco products. It is very easy for a new user of an E-Cigarette to incorrectly attribute these quitting smoking side effects to the E-Cigarette, when in fact they are likely the result of your bodies reaction to quitting smoking tobacco cigarettes.
Side effects of quitting smoking include: Bad breath, stomach pain, nausea, constipation, increased appetite, skin breakout’s increased coughing, insomnia, depression, vagueness, irritability, gas, dry throat, nasal drip, dizziness, vertigo. Many of these side effects of quitting smoking will be alleviated by using the E-Cigarette.