Norma,
I also have fibromyalgia which causes chemical sensativity. I react to things I have safely taken for years as well as detergents and such. I called my Rheumatologist and asked him about the potential meds for graves and what he thought given my history. He told me the the anti-thyroid drugs can cause hives and that as a result of my chemical sensativity I should not take them.
Good luck with the new med I hope it works and oatmeal baths (you can buy the packages in the drug store) really helps the itching until the hives goes away.
Diane