Carbon Dioxide Relieves Allergy Symptoms

Carbon dioxide (CO2) pumped intranasally so that it flows into one nostril, through the sinus cavity, and out the other nostril provides significant relief from the nasal symptoms of seasonal allergic rhinitis for up to 24 hours, according to a new study.

Researchers at Creighton University Medical Center (Omaha, NE, USA) conducted the study, in which 89 patients were randomized to receive either CO2 or dry air as placebo in two 60-second applications. The patients were adults with at least a two-year history of medicated seasonal allergic rhinitis and a positive skin prick test to seasonal grass or mold allergens. Patients were excluded if they had asthma (other than mild intermittent), were on concomitant medications, had significant nasal disorders, an upper respiratory tract infection within 14 days, or rhinitis medicamentosa.

The investigators found that carbon dioxide significantly improved total nasal symptoms scores compared with placebo. The improvement from baseline was significant at 10 minutes and continued for 24 hours. The treatment had no effect on non-nasal symptoms of seasonal allergic rhinitis, however. The treatment was found to activate the trigeminal nerve and inhibit the release of a calcitonin gene-related peptide (CGRP), a peptide that causes vasodilation and glandular secretion, potentially contributing to nasal symptoms and rhinorrhea seen with allergic rhinitis. The results were presented at the annual meeting of the American Academy of Allergy, Asthma, and Immunology in March 2006 in Miami (Florida, USA).

"It can be used repeatedly and it's very safe,” said study co-author F. Tony Romero, M.S. "It's an exogenous molecule that we give out ourselves.”



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