Sheiky-Baby posted...
More concentrated nicotine, or/and unknown amount of additional chemicals and shit they put in them.
It's the nicotine. Same thing happens to those who aren't experienced with nicotine when they take it via any means; same thing happens to experienced smokers who suddenly smoke more cigs in a short time than they're used to. Vapes, especially pods / disposables, do contain pretty high levels, and users often tend to consume more than they would of a cigarette even accounting for this difference in nicotine level.