Cytomel and hives

I have been taking synthroid and cytomel for years now. Had hyperthyroidism (Grave's disease), had radioactive iodine treatment to leave me without a thyroid. About 6 months ago, I started getting hives. Doctors at first thought it was stress. I am not allergic to anything. The only medicines that I take on a regular basis are synthroid and cytomel. I think it might be because of these drugs but not sure. I have made an appointment to see my internist.

I am a 19yr old female athlete w/Hashimoto's. When .1synthroid did not seem to be controlling my hypothyroid symptoms (hair loss, wt gain, fatigue), my dr. tried 5mcg of Cytomel twice/day. At first I didn't notice much of a change...slowly side effects appeared. I developed rashes and itchy hands, especially after exercise...finally got heart palpitations and ended up in the hospital with anaphalactic shock (probably due to these effects combined with mono -undiagnosed at the time). I am now off of Cytomel, and dr is changing me from Synthroid to Levoxyl thinking that I might have an allergic reaction to something in the Synthroid also, as I have been breaking out in hives after exercise,since I started taking it. Has anyone else experienced these symptoms? Anyone had success with Levoxyl? VERY FRUSTRATED!!!