I am not sure whether we have such things here, but I do have a Cave penicillin, Morphine and I forget which else engraved on a tag on my keyring. Also my ID card has full details but more importantly the emergency services can check my ID card for all allergens.
The first thing that the emergency services do, apart from life-saving stuff, is check for my ID card, which by law has to be carried with you all the time. And that will instantly bring up all medical details.
I know that many people do not like the idea of ID cards but mine has saved my life more than a few times by bringing up life-threatening allergens.