Eucalyptus as a specific irritant causing vocal cord dysfunction

Background: Vocal cord dysfunction (VCD) is a well-recognized clinical entity that frequently mimics asthma and is characterized by inappropriate adduction of the vocal cords during inspiration. The pathogenesis of VCD has not yet been defined. The only previous report suggested that respiratory irritants may trigger paradoxical motion of the vocal cords. Objective: To report the case of a 46-year-old woman with VCD precipitated by eucalyptus exposure. Methods: A masked flexible fiberoptic nasolaryngoscopy was performed to confirm whether VCD occurred with eucalyptus and not with other known respiratory irritants. The patient underwent inhalation challenges consisting of water, ammonia, pine oil, and a combination of eucalyptus (dried leaves) and ammonia. Two independent observers before patient challenge could not identify eucalyptus. Results: Vocal cord dysfunction occurred within minutes of exposure to eucalyptus. This is the first report to prospectively document that a specific irritant, eucalyptus, can precipitate VCD. Negative skin prick test results, total IgE level, and negative IgE eucalyptus-specific antibodies support a nonimmunologic mechanism. Conclusions: A new pathogenic mechanism for this clinical entity is supported by our observations. Furthermore, a nonimmunologic mechanism in which respiratory irritants may induce VCD is suspected. Future studies to elucidate this mechanism need to be performed in individuals with irritant-specific VCD.