Some side-effects noted by e-smokers: Weight gain, notably, wallet has more money in it and weighs you down. Smoking indoors increased, irreparably harming people nearby with nontoxic vapor. Increased USB power consumption. Feelings of fraud/enlightenment when smoking near people using actual cigarettes. Ability to run without wheezing. If wallet gets too heavy to carry consult your doctor or accountant. all kidding aside there are some side effects and they are dependent on the user 1. could have slight sore throat, (adjust the PG/VG RATIO, pg can cause sore throat) 2. acne break out ( could be from pg, but for most it goes away after quitting smoking in about a month, some depending on person can still have breakouts) 3. Allergic to PG OR VG, you would know from a rash, hives, etc symptoms of being allergic. 4. light headed or dizzy? (this could be to high of nic, lower your nicotine) If you have problems with health that were not present before you should quit vaping until you have seen or spoke to a doctor Always listen to your body. Every one is different with their limits of use if you know of other common side effects that have occurred with you please post and write if it changed and what you did to avoid it, also always drink water, and keep hydrated when vaping, the fluid can also help with any mild sore throat.