I was wondering the same thing this past weekend. I normally inhale into my mouth, then inhale into lungs... just like I did when I used to smoke. I tired this past weekend with 3 different juices to just hold vapor in my mouth, and then "exhale" through nose. HORRIBLE!! The vapor was very rough. It burned my nose, throat, etc. When I inhale into my lungs and then do a nasal exhale, all that roughness is gone. So my theory is that something is being absorbed by the lungs. I'm guessing that "roughness" is the nicotine (18mg). So while I'm not disputing that you can get the nicotine from your mouth/nasal membranes, I believe it is also entering through the lungs. Just my opinion.