Hi, I am not sure at all but am extremely well-versed with allergic anaphylaxis and food allergies because my daughter is anaphylactic to latex, plums, nuts and has been in the ER two times and carries an epi pen.
If this sheds no answers, I'd consider a good allergist and get tested. If it still continues outside of the thyroid, maybe under your Dr do a total food elimination diet and add in one thing a time until you see a small reaction begin and you may uncover your culprit if it isn't thyroid related.
I really am not sure on the hives and hypothyroid . you could also try to get onto Dr. Lupo's expert forum
http://www.medhelp.org/forums/show/120
WELCOME to the community.
I had some instances of hives out of the blue and am not an allergy person .. turns out my Vitamin D was extremely low and am now being treated. It was 9 when normal is 32-100. I'd ask them to toss in a Vit D test also.
Regards,
C~
partial thyroidectomy 1/07
TSH 1.8