hives caused by thyroid pills--even after stopping, the hives persist

I was diagnosed with low thyroid in Dec 08 and started on a low dose of armour thyroid. Several weeks later I developed hives on my arms. I was switched to a synthetic thyroid pill but the hives came back. I switched to Iodoral but they came back even worse.I stopped all medication, including my omega three pills, but the hives persisted. Now if I eat any food with iodine, even so much as a bite of store-bought bread, they come back all over my arms, hands, feet, stomach, and legs. They start when I wake up and are usually gone by early afternoon.

I am 50 years old and have never had hives in my life before, or any skin condition. I don't know how just a few weeks of thyroid medication could have caused such a sudden and profound intolerance to iodine. My doctor is baffled and I don't know what to do.