Treatment of urticaria. An evidence-based evaluation of antihistamines

Urticaria is a cutaneous syndrome characterized by dermal edema (wheal) and erythema (flare) that blanches with pressure. The lesions typically last less than 24 hours and are usually pruritic. In 1983, Christensen and Maibach summarized the theory behind the use of histamine H1 receptor antagonists (antihistamines) in clinical dermatology. These agents remain the mainstay of treatment for urticaria. This article reviews the medical literature on the effectiveness of antihistamines in urticarial syndromes, including acute, chronic idiopathic and the physical urticarias. Older antihistamines, such as chlorpheniramine and hydroxyzine, are effective in the treatment of urticarias, but they also have marked sedative and anticholinergic effects. Newer nonsedating antihistamines (second-generation antihistamines) have been developed that have reduced adverse effects because they do not cross the blood-brain barrier; these agents (acrivastine, cetirizine, loratadine, mizolastine, fexofenadine, ebastine, azelastine and epinastine) cause significantly less sedation and psychomotor impairment than their older counterparts. A review of the literature reveals that there are few studies which document the efficacy of second-generation antihistamines in the treatment of acute urticaria, a biologic entity that usually resolves within 3 weeks. We did not identify controlled studies that suggested superiority of any antihistamine in the treatment of acute urticaria. Loratadine or cetirizine, and possibly mizolastine, appear to be treatments of choice for chronic idiopathic urticaria. For symptomatic dermatographism, the combination of an antihistamine and an H2 antagonist, e.g. chlorpheniramine and cimetidine, appears to be effective. Very few studies have been conducted on the use of antihistamines in the treatment of cold, cholinergic, and pressure urticaria. Antihistamines are the mainstay of urticarial therapy. This evidence-based review suggests that there are efficacy differences between newer, nonsedating antihistamines and older agents in some forms of the disorder. Clearly, further well-controlled clinical trials in larger numbers of patients are needed to clarify the role of these agents in the treatment of urticaria.