A friend has the misfortune to have an intolerance to any and all egg products. She found out (the hard way) that many people think "intolerance" means "I can't have very much of it" and switched to saying "allergy" even though this is technically incorrect.
Also, she found out that apparently "any part of the egg at all" does not seem to include the white: "oh, there wasn't any yolk in it so I thought you'd be ok" - well, you thought wrong...
And so forth.

As for me, I can't eat blackcurrants without being very unwell. It's not a big issue, but I feel for thouse with more major issues:
Q. What fruit is on today's fruit cheesecake?
A. I don't know. Does it matter?
Q. Is there any bleackcurrant in this?
A. I don't know. Does it matter?
(nb - to stand a chance of a correct answer, ask an open question without giving them a clue what answer is better.)
Q. So, Ian, is it the flesh of the fruit that causes you to be unwell or the juice?
A. I have no idea, and I don't wish to be violently ill while I experiment on this one. Omitting all blackcurrant from my diet is just fine.
Q. Are you sure you can't eat blackcurrants?
A. Yes, quite sure, thank you.
et cetera, ad nauseam, literally sometimes...