We describe below two patients who presented with thyrotoxicosis and were put on carbimazole treatment. Both of them developed urticarial rash following commencement of carbimazole treatment. The drug was stopped but the patients continued to have the rash for a few months. One patient became biochemically hypothyroid despite cessation of treatment but again became biochemically and clinically hyperthyroid and subsequently underwent radioactive iodine treatment. The other patient was treated with propylthiouracil and became euthyroid. It was found that the urticaria improved in both patients as their overactive thyroid status got better.