We assessed the effect of dry air (DA) nasal breathing on nasal clearance rate in healthy nonsmoking subjects. We measured saccharin nasal transit time (SNTT), an index of mucociliary clearance rate, in eleven normal subjects (six males, five females) breathing either room air (RA) or DA through the nose in random order on six different study days. On each study day, the trial was conducted at the same time, in the same nostril, using a patent airway. DA was breathed through a light-weight, tight-fitting, nasal mask (SEFAM, France) for 30 min and SNTT was then measured immediately. Saccharin (250 micrograms) was deposited on the anterior part of the inferior turbinate under visual control and saliva was swallowed every 30 s thereafter. SNTT was the time elapsed between deposition and first perception of saccharin taste. The group-average SNTT on DA was 18.5 +/- 8.6 min which was significantly longer than on RA (11.9 +/- 5.3 min). Our findings suggest that dry air breathing results in excessive water loss by the nasal mucosa, which may in turn reduce nasal mucociliary clearance rate through changes in the rheological properties or adhesiveness of nasal mucus and/or slowing of ciliary beating.