To think I wasn’t in the wrong for not mentioning my allergy?

[ChiChaNaYubi]

My sister in law made a birthday cake for our father in laws birthday yesterday.
Turns out she used duck eggs in the batter, which make me violently sick and give me breathing problems. I wasn’t mad about it, I understand it’s a really odd thing to be allergic too but she’s absolutely livid with me for not telling her. Thing is, it just never occurred to me to ask tbh! It’s such a random allergy that I often forget about it as duck eggs are just not something I ever come across really. She been really quite nasty to me about it, calling me thick, irresponsible etc.

Is she being u reasonable to be so angry or am I for not asking ?

Although the AIBU is clearly "should OP have told SIL about the allergy", it's really the SIL's reaction that's so unexpected - calling her thick! That is unreasonable given that the OP wasn't blaming her.

I don't know. Obviously SIL shouldn't be name calling, but if you were driving and ran someone over because they stepped out in front of you....even if they were ok and didn't blame you, its normal enough to feel horribly guilty and, yes, a bit angry at them too I think...so I don't think SIL being angry is unexpected really.

Again, SIL shouldn't be name calling of course (though I'd understand a heat of the moment and apologse afterwards sort of thing, which I don't think is the case here).

As someone who deals with allergies all the time OP was definitely irresponsible, but making a stupid mistake doesn’t make you thick, just human. But I really think you need to start carrying an epipen if you're having breathing problems when you eat the wrong thing by accident, OP. It's a serious condition.