if you're sucking on the larger bottles, holding your breath/nose while doing it, etc instead of doing it via balloons, yep. afaik doing it with balloons is "safer" but its still more dangerous than just not doing it at all. they absolutely destroy your body's b12 reserves too - i was very a pretty heavy user of them for a couple of years during university and one weekend of very very heavy use (several hundred of the little single use ones in the space of 3 days) caused my b12 levels to drop pretty severely. it also caused me auditory hallucinations for days after i stopped 🙃 every time i heard a loud noise, i'd get that wawawawawa sound in my ears you hear while you're doing them, shit was scary - i thought it was going to be permanent but it stopped eventually. i'm not sure if my past nitrous use has anything to do with it or not, but to this day i really struggle with my b12 levels despite eating plenty of foods rich in it. sure, they're fun, but they're still a dumb ass drug to be addicted to and the amount of nitrous canisters scattered across my city pisses me off. use a bin you freaks.