hyperthyroidism
"After being diagnosed with Grave's Disease, my doctor prescribed methimazole to bridge my symptoms until my procedure to "kill" my thyroid.  I noticed I no longer had extreme stomach pains and the shaking improved considerably.  However, after a month of being on the medication I broke out in itchy, uncontrollable hives.  Benadryl didn't even get rid of them.  Once I stopped taking methimazole they went away after about 48 hours but the itching was still prevalent.  Now my stomach pains are back and the shaking is worse."