In terms of the harm to the user: nitrous oxide oxidises the cobalt in cobalamin (B12), rendering it inactive. Serious B12 deficiency from heavy use over a long

In terms of the harm to the user: nitrous oxide oxidises the cobalt in cobalamin (B12), rendering it inactive. Serious B12 deficiency from heavy use over a long period of time can (and does in practice, although not necessarily that commonly) cause permanent disability (neurological damage, leading to weakness etc...). It can also cause more acute harm if people inhale it without enough oxygen. Going after users is unlikely to be a net positive for harm reduction, compared to increasing education on the risks, and maybe some kind of regulation on how and where it is sold.