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.