The role of antihistamines in upper respiratory tract infections

Abstract

Antihistamines are commonly administered for URI, but their efficacy cannot be easily demonstrated. Three placebo-controlled, double-blind studies identified either a slight or no beneficial effect of oral (chlorpheniramine and terfenadine) and nasal (diphenhydramine) antihistamines on mild and moderately ill patients with URI. One reason for this lack of effect is that unlike other mediators (e.g., kinins, albumin, and neutrophils) that have been found to correlate with symptoms of URI, histamine is not present in increased concentrations in persons with URI. Viruses can induce histamine release from basophils during subsequent exposure to antigens. Some studies have shown that this mechanism is mediated by interferon. Histamine release independent of antigen challenge has not been demonstrated. Some infected persons manifest the production of virusspecific IgE antibodies; this is most common in the nasopharyngeal secretions of patients with wheezing. Histamine and LTC4 have been noted in higher concentrations in these patients than in patients infected without wheezing. This subpopulation of virusspecific IgE responders may be candidates for antihistamine therapy. Antihistamines are commonly used to treat URIs. This article explores the effectiveness of antihistamines in URI. It also reviews studies designed to determine which mediators are important in causing the symptoms of URI. Finally, it describes the formation of virus-specific IgE and the release of such chemical mediators into the airway at the time of viral infection.