This happened a few years ago, but this morning's breakfast reminded me about it.
I got into a disagreement over walnuts. I can eat English walnuts, but Black walnuts make my mouth itch, my tongue tingle, GI symptoms, and my chest feel slightly tight (also, I just feel bad for the next day or so). I had someone arguing with me that walnuts are walnuts, so if I react to one variety, I should react to them all. I do agree that it seems strange that I can eat one kind but not the other. I'm not allergic to any other tree nuts and actually often forget that I have this one weird reaction unless I see Black walnuts. Then it's like, oh yeah, I shouldn't eat those.
Has anyone else had any experience like this or known someone who has? I cannot seem to find a logical explanation as to why Black walnuts give me an allergy response, but English walnuts do not. Yet that is the case. It's their some kind of actual difference between the two that I just don't know about?