IgE-mediated allergy to chlorhexidine

Background: Investigations at the Danish Anesthesia Allergy Centre have included testing for allergy to chlorhexidine since 1999. Objective: To investigate whether measurement of IgE and histamine release confirm an IgE-mediated mechanism for chlorhexidine allergy. Methods: Twenty-two patients with clinical history suggestive of chlorhexidine allergy were included. Skin tests with chlorhexidine and tryptase measurements were performed during initial investigations. Sera were analyzed retrospectively for IgE and histamine release (passive sensitization) to chlorhexidine. Results: Twelve patients were skin test positive and 10 were skin test negative. Of the skin test-positive patients, 11 of 12 had IgE to chlorhexidine and 7 of 11 had a positive histamine release test. None of the skin test-negative patients had specific IgE or positive histamine release to chlorhexidine. Skin test-positive patients had higher median age (64 vs 49 y) and were mainly male (11/12 vs 6/10). In both groups, 8 patients had hypotension, but bronchospasm mainly appeared in skin test-negative patients (1/12 vs 6/10). Reactions occurred more often during urologic surgery in skin test-positive patients (5/12 vs 0/10). Baseline tryptase was higher in skin test-positive patients (median, 11.5 vs 3.7 mu g/L), and 6 of 7 patients had elevated IgE to chlorhexidine in serum at the time of reaction. Conclusion: This study confirms that chlorhexidine allergy is IgE-mediated and that measurement of specific IgE and histamine release are good adjuncts to skin testing in patients with clinical history suggesting chlorhexidine allergy. Clinical implications: IgE and histamine release can be used to support the diagnosis of allergy to chlorhexidine.