Man, I say this a lot and I know it comes across standoffish, but... US ethnic categorizations seem bonkers to me.
What does "half Jewish half Irish" even mean? Isn't that a Jewish person from Ireland? That would count as fully both things. What are the other two halves?
This is why I have to think about the immigration form for ten minutes each time I get through customs in the US, it's all "was any of your grandparents a smurf?" and "are you latino and/or lactose intolerant?" and stuff like that. It makes no sense.
So wait, how does a nickel allergy work? Like, if they rake your leaves and you're like "thanks a bunch, here's some change for your hard work", do they die Killer Bean style?