Thing is, though-- I'm pretty confident saying that the Wendy's item wasn't shellfish contaminated. They don't handle crustaceans on the premises-- it's one of my family's go-to fast food options for that reason.
I'd also expect (based upon that kind of sensitivity and apparent severity) that you
would have had other symptoms periodically which would correlate with contaminated food (shared fryers, grills, etc. or just processed food that is cross-contaminated with shared production spaces).
To
never have symptoms more typically associated with food allergy (cutaneous or GI) would also be exceedingly strange-- and also know that
usually, even fairly severe symptoms tend to resolve rather quickly (1-6 hours, usually)-- outside of protracted anaphylaxis that can last for days. That kind of protracted anaphylaxis is fairly unusual-- especially on more than one occasion.
So those aspects of things don't fit food allergy particularly well. It's also the sum of
several very unusual/rare manifestations of food allergy that makes me suggest that it is probably
not a shellfish allergy-- but it's coincidence enough that it'd be worth getting tested, that much is certain. Do you have an allergist?
My concern is that without a clear yes/no re: food allergy, you may wind up ignoring something serious like
TIA, or something in the pathology list
here.
Those things can result in episodes like those you mention.