I'm allergic to penicillin, the antibiotic. I just got a new (European) passport. Is there some 'best practices'/common way to mark this allergy on my passport? I filled in the emergency contact & blood group details, so I wonder if I should put penicillin allergy down? Is there any commonly understood code/symbol/wording? Or should I just write "PENICILLIN ALLERGY" (and whatever that is in French) on the same page as the blood group details?
I wouldn't count on your passport being something other people looked at when deciding to treat you. In Canada people use MedicAlert bracelets for this purpose - according to their website they're international.
Really important things like allergies are engraved on the back, and there's a code that hospitals can use when they phone, and they can get more details.
Do NOT write in your passport, apart from the fields specified. Any additional marking that isn't done by passport officials can cause you problems at borders - I've seen it happen first hand :/
Also - as @Kate says, a medical staff member is unlikely to look at your passport for such things. In general, best practice is to get a Medic Alert wrist bracelet or necklace (I've got the bracelet) and it comes with a card that you can put in your wallet.
Medical staff are far more likely to look at a medical bracelet, or search your wallet for information, than to look in a book that is specifically for border crossings. You may get lucky, but I'd be more inclined to suggest the others instead.
I've had my Medic Alert bracelet looked at / recognised by medical staff in five continents, so it seems pretty international, and hard to miss. I don't even notice that I wear it any more.
Well, when a patient has penicillin allergy in a hospital, we always write
Sine Penicillium on their bed sheet, which gives an information to any medical professional that the patient is not to be given any of the antibiotics from the penicillin strand.
But it is true, an EMT or a doctor wouldn't look into your passport to check about your medical conditions. You can either have a bracelet and a card in your wallet (as mentioned) or a small tattoo in your chest area or your arm.
Mind you, if you do have a bracelet, try and get it in Latin, even though English is fine as well.