Thanks for your comments. You describe a condition called chronic urticaria and the blood test that allergists/immunologists sometimes order is looking for an antibody against the high affinity IgE receptor. This is an autoantibody that is sometimes seen in patients with chronic urticaria. Some patients with this type of hives could have relief from antihistamines, and some may need more powerful therapies like taking oral steroids as you have done.
However, it may be to your benefit to discuss with your physicians (dermatologist or allergist) the possibility of trying steroid sparing agents, so that you may not need to take oral steroids that often. Most allergists would not consider the steroid courses as an optimal long term treatment for chronic hives, so it is quite likely that choosing a more long-term treatment will be the next thing they will want to discuss with you. Long term steroid use can have some detrimental effects, so I hope you don't have to use them that often.
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