Chronic urticaria: aetiology, management and current and future treatment options.
Chronic urticaria is a common condition that can be very disabling when severe. A cause for chronic idiopathic urticaria (CIU) is only infrequently identified. Potential causes include reactions to food and drugs, infections (rarely) and, apart from an increased incidence of thyroid disease, uncomplicated urticaria is not usually associated with underlying systemic disease or malignancy. About one-third of patients with CIU have circulating functional autoantibodies against the high affinity IgE receptor or against IgE, although it is not known why such antibodies are produced, or how the presence of such antibodies alters the course of the disease or response to treatment. There are only a few publications relating to childhood urticaria, but it is probably similar to the adult form, except that adult urticaria is more common. The diagnosis is based on patient history and it is vital to spend time documenting this in detail. Extensive laboratory tests are not required in the vast majority of patients. Chronic urticaria resolves spontaneously in 30-55% of patients within 5 years, but it can persist for many years. Treatment is aimed firstly at avoiding underlying causative or exacerbating factors. Histamine H1 receptor antagonists remain the mainstay of oral treatment for all forms of urticaria. The newer low-sedating antihistamines desloratadine, fexofenadine, levocetirizine and mizolastine should be tried first. Sedating antihistamines have more adverse effects but are useful if symptoms are causing sleep disturbance. Low-dose dopexin is effective and especially suitable for patients with associated depression. There is controversy as to whether the addition of an histamine H2 receptor antagonist or a leukotriene antagonist is helpful. For CIU, second-line agents include ciclosporin (cyclosporine) [which is effective in approximately 75% of patients], short courses of oral corticosteroids, intravenous immunoglobulins and plasmapheresis, although the last two were found to be beneficial in small trials only. Treatments for CIU with only limited or anecdotal supportive evidence include sulphasalazine, methotrexate, stanazol, rofecoxib and cyclophosphamide. The efficacy of photo(chemo)therapy is controversial. Physical urticarias may respond to H1 receptor antagonists, although in delayed pressure urticaria, and cold, solar and aquagenic urticaria, the response may be disappointing. Second-line agents for physical urticarias vary depending on the urticaria and most have limited supportive evidence. The potential for spontaneous resolution, the variation in the disease activity and the unpredictable nature of the disease makes the efficacy of treatments difficult to assess.