Okay, so maybe this article is going to be a bit tongue-in-cheek. Nevertheless, we'd like to submit to you the idea that in ultra-rare circumstances, bad breath might end up contributing to an untimely death or two, however indirect the connection may be.
Consider a couple of episodes from the Spike TV docu-fiction series 1,000 Ways to Die. This show, which is more than a little facetious itself, has twice related tales of individuals dying because of bad breath. Whether the stories are real or credible is up for debate.
The first appeared in the show's 16th episode. In it, the narrator relates a tale that reportedly took place in Miami, Florida: A woman is tied to a chair by a burglar, and her mouth is taped over. The intruder's halitosis supposedly makes the woman sick, with lethal results.
In the second such story (again, quite possibly an urban legend), reporters tackled the case of a lecherous male nurse who targets older patients. After kissing an elderly women with exceptionally bad breath, the nurse runs to the bathroom and ingests denture whitening tablets and a glass of denture cleaner (which he mistakes for breath mints and water). The resulting digestive effects are deadly.
Now, it is very unlikely that either of these events ever actually took place. The show is known to bend facts in the service of artistic license. For the most part, oral odor on its own could almost certainly never be lethal, and if it was, sales of specialty breath freshening products would soar even higher.
In fact, the only way that bad breath could be a direct cause of death would be if the volatile sulfur compounds that created the odor (like hydrogen sulfide) were so thick that they outright poisoned anyone in smelling range.
However, the Environmental Protection Agency estimates that the concentration of hydrogen sulfide found in halitosis would need to be about 200,000 times stronger in order to be deadly.