Hives.....
Hives are one of those thing that can have myriad causes -- a virus, an allergic reaction, etc. I just got over a case of hives -- who knows? I also had an ear infection -- so maybe it was viral, and maybe it was an allergic reaction to several days of shrimp.
Take benadryl and go to the doctor. They will give you a shot and sterioids. That should do the trick!
Get lots of anti-itch cream too!