From what I understand, stress can makes our allergic reactions worsen. I have an allergy that the docs have not been able to figure out yet, I am treated the same as you and now have an EPI pen.
As I am not a doctor, but I think when you have an allergy to something, the stress can make it worse.
My last trip to the hospital I had the same itchy, hives, swelling, that you had, I am sure that is just part of the allergic reaction as the meds fixed my issues also.
They say we can not be allergic to stress, but we are all different.
May be a great idea to keep a diary of activities and food, etc and see when these reactions occur.