Comparison of nasal mucosal responsiveness to neuronal stimulation in non-allergic and allergic rhinitis: effects of capsaicin nasal challenge.

BACKGROUND: Neuronal involvement has been implicated in the pathophysiology of non-allergic and allergic rhinitis, contributing to the typical exacerbation of these conditions upon exposure to non-specific environmental irritants.
OBJECTIVES: To determine if non-allergic and allergic rhinitis are characterized by increased responsiveness of the nasal mucosa to sensorineural stimulation.
METHODS: Nasal challenges with capsaicin and its vehicle were performed in three groups of subjects -- non-allergic rhinitics, perennial allergic rhinitics, and healthy controls -- and resultant symptom scores, glandular secretion reflected by lactoferrin levels, and plasma extravasation reflected by albumin levels in nasal lavage fluid were compared.
RESULTS: Capsaicin-sensitive nerve stimulation produced increases in symptom scores and lactoferrin levels which were similar among the three groups of subjects. On the other hand, only the group of subjects with allergic rhinitis demonstrated a significant capsaicin-induced increase in albumin levels and a trend in total protein levels.
CONCLUSIONS: We conclude that non-allergic rhinitis is not characterized by increased responsiveness of capsaicin-sensitive nerve fibres; while allergic rhinitis is marked by hyperresponsiveness manifested as increased albumin leakage in nasal fluids. This may reflect the activity of an axonal reflex to sensorineural stimulation.