Evidence for primary laryngeal inhalant allergy: a randomized, double-blinded crossover study.

Background: Despite anecdotal reports, no controlled studies to date link allergen exposure with a change in vocal function or dysphonia. The aim of this study was to determine whether allergen exposure in susceptible individuals impairs vocal function.

Methods: The study was a prospective, double-blind, placebo-controlled study in which subjects serve as their own controls. The participants were 5 inhalant allergic adults with suspected dysphonia from allergies, without evidence of reactive lower airways based on methacholine challenge. All subjects were exposed to 2 experimental conditions in which they were challenged with (1) orally inhaled diluent placebo on 1 day, and (2) orally inhaled allergen on another day. Conditions were randomly ordered across subjects and separated by at least 48 hours. Phonatory threshold pressure (PTP) at the 80th percentile pitch was measured prior to diluent and allergen challenge, and 15 and 60 minutes postchallenge to assess potential change in vocal function after challenge testing.

Results: A repeated measures ANOVA revealed a significant main effect for treatment (allergen vs placebo, p = 0.013) with greater PTP required post-allergen challenge compared to placebo and an effect size of 0.821.

Conclusion: A primary causal relationship between allergen exposure and impaired vocal function, as assessed by PTP, was observed in adults with documented allergy independent of asthma or nasal exposure. The current design establishes a safe model for laryngeal inhalant allergen challenge.