I think it's the nicotine ... and the stronger the cigar, the more truth there is in it ... there is, I think, a certain 'immunity' to be built up so more experienced smokers are less easily affected than those who've not smoked much ...
I hadn't experienced that sort of sensation in years until this last November when I learned that a Joya de Nicaragua Antano torp isn't the best choice for an after breakfast morning smoke on a morning one has skipped breakfast ... the effect was so great, I was not only horribly nauseated, but in a profuse sweat and apparently quite pale looking .... we were on the freeway, but traffic was quite heavy and we were not at high speed, so I couldn't even catch much of a breeze ... MrsS suggested tossing the cigar since it was having such an incredible effect on me, but I said "hell no, this smoke is too great for that!!!" ...
did I mention that cigar smokers are a peculiar sort?? ... yeah, we must be ... that smoke was so damn good, it was making me sick to my stomach, shake like a leaf in the breeze and perspire so greatly it looked as if a bucket of water had been poured over me .... what would make her sugest I might want to toss it out the window ??? And guys I've told of my experience asked only "what kind of cigar was that again??? ... I've gotta TRY one of those!!!"