Sulfur dioxide does not acutely increase nasal symptoms or nasal resistance in subjects with rhinitis or in subjects with bronchial responsiveness to sulfur dioxide.

We examined whether brief exposures to moderately high concentrations of sulfur dioxide (SO2) causes acute increases in nasal symptoms and nasal resistance in subjects with chronic rhinitis. We studied 19 subjects with allergic rhinitis and 3 subjects with chronic intermittent rhinorrhea, nasal congestion, and sneezing without any other manifestation of allergy. We found that the change in nasal resistance and symptoms caused by nasal inhalation of 4 ppm of SO2 for 10 min was no greater than the changes caused by nasal inhalation of conditioned room air. In a second set of experiments, we examined whether allergic subjects with demonstrable bronchomotor responsiveness to SO2 also had nasal responsiveness to the gas. We studied 8 subjects with a history of both asthma and allergic rhinitis. Each subject developed symptoms of dyspnea or wheezing and an increase in specific airway resistance of at least 8 L x cm H2O/L/s after breathing 1 or 2 ppm of SO2 by mouthpiece at 20 L/min, and did not develop these changes after breathing room air under the same conditions. No subject, however, developed more nasal symptoms or a greater increase in nasal airway resistance after tidally breathing SO2 through the nose than after breathing room air, even when the concentration of SO2 delivered to the nose was double the concentration delivered through the mouthpiece to the lower airways. We conclude that brief exposure to SO2 at a concentration of 4 ppm or less is unlikely to cause significant nasal dysfunction in most subjects with chronic rhinitis, and that in subjects with both allergic rhinitis and asthma, responsiveness to SO2 is not uniform throughout the respiratory tract.