Urticaria. Recognition, causes and treatment.

The urticarias are a complex group of disorders characterised by transient whealing or swelling of the skin. Understanding the many possible causes is the first step in assessing urticaria. Allergic and drug-induced urticaria respond to removal of the cause. The physical urticarias, particularly delayed pressure urticaria and also urticarial vasculitis, require separate consideration. For the majority of patients with chronic idiopathic urticaria, nonsedating antihistamines are the mainstay of treatment. There are several to choose from, including cetirizine, astemizole, loratadine, terfenadine and acrivastine, each with its own pharmacokinetics and antiallergic properties. When these fail, histamine H2-antagonists may help either alone or in combination with H1-antagonists. Older sedative antihistamines are still useful. Ketotifen, oxatomide and azelastine have mast cell stabilising effects that are considered an advantage in treating these disorders. Second-line therapies include a wide range of drugs such as doxepin, dapsone, attenuated androgens, calcium antagonists, antimalarials, gold and methotrexate. The most effective and regularly used second-line agents are corticosteroids. These are best limited to short term crisis management, except in severe recalcitrant cases, and in patients with pressure urticaria or urticarial vasculitis. Recent work on circulating histamine releasing autoantibodies suggests that there is scope for more aggressive immunosuppression in selected patients. However, effective treatment with immunosuppression often requires plasma exchange and more toxic agents such as cyclosporin. Such treatments are only likely to be entertained in exceptional cases.