What are investigations done for urticaria?

• In most cases of urticaria, there is no need for specific investigations. However, the following tests may be helpful in some cases: • Full blood count to identify eosinophilia caused by allergy or parasitic infestation, and low WBC from systemic lupus erythematosus • Thyroid antibodies and function in chronic urticaria • Complement tests in case of angioedema without urticaria or urticarial vasculitis • Skin biopsy if wheals are prolonged, to identify vasculitis