Abstract
Betel (areca) nuts are extensively chewed in many countries. This has been associated with respiratory symptoms. We aimed to determine whether betel nut chewing is associated with acute changes in fractional exhaled nitric oxide, a non-invasive marker of airway inflammation. Betel nut chewing resulted in an immediate significant decline in fractional exhaled nitric oxide levels that persisted for up to 180 minutes. This effect has to be taken into account in epidemiological studies, reference ranges, and patient preparation.