Once you have quit smoking completely, the lungs begin to heal themselves, primarily by reproducing the tiny hair-like structures called "celia" which remove foreign materials from our lungs. Smoke ......s the production of celia. The cilia help the lungs to remove mucous or phlegm which is normally produced to help remove foreign or unwanted contaminents. Your lungs are beginning to return to normal and trying to remove the harmful stuff you got from smoking.
Pg and Vg (propylene glycol and vegetable glycerin) are considered to be humectants, meaning that they attract water. Inhaling vapor with the byproducts of Pg & Vg likely absorbs an amount of water from the lungs, so it is very important to stay well hydrated by drinking plenty of water.