Does nitrogen dioxide affect inflammatory markers after nasal allergen challenge?

Exposure to high ambient levels of nitrogen dioxide (NO2) enhances the bronchial inflammatory reaction to allergen in humans. We tested whether this NO2 effect occurs also in the upper airways.

Sixteen allergic subjects with rhinitis and mild asthma were exposed at rest to either purified air or 500 microg/m3 NO2 for 30 minutes, followed 4 hours later by a nasal allergen challenge. Nasal lavage was performed before air/NO2 exposure, before allergen challenge, and 1, 4 and 18 hours after allergen challenge. Symptoms were recorded.

The percentage of eosinophils and neutrophils, eosinophil cationic protein, and myeloperoxidase were similar after exposure to air + allergen and to NO2 + allergen. We noticed a tendency to increased sneezing the day after exposure to NO2 + allergen.

The priming effect of an ambient brief NO2 exposure on subsequent allergic response was not noticeable in activation of inflammatory cells and mediators in the upper airways.