Nasal saline irrigation has no effect on normal olfaction: a prospective randomized trial.

BACKGROUND

Nasal saline irrigation is a safe treatment for chronic rhinosinusitis; however, its effect on olfaction is unclear. Cyclic adenosine monophosphate (cAMP) is a key second messenger in the mechanism of olfaction and has been shown to be associated with smell function. In animal studies, olfactory cilia may be harvested by simple saline preparations. This study aimed to characterize the effect of nasal saline irrigation on smell function.

METHODS

Volunteers with normal olfaction were randomized into a control or irrigation cohort. In the initial appointment, subjects completed a University of Pennsylvania Smell Identification Test (UPSIT) and nasal samples were obtained by 2 methods: the nasal curette and cytobrush. The irrigation cohort performed daily nasal saline irrigations. Both cohorts then returned in 1 week. The UPSIT and nasal cell collection were repeated, and each subject completed a subjective olfactory transition scale. Nasal samples were processed for cAMP levels using a commercial assay.

RESULTS

Thirty-two subjects were enrolled and randomized into each cohort. Control and postirrigation mean UPSIT scores were 36.8 and 36.7 (p = 0.48). No subjects reported a subjective smell loss. Ten pairs of nasal samples were assayed. Using the curette, control and postirrigation cAMP levels were 509 and 490 fmol/(mg/mL), respectively (p = 0.94). Using the cytobrush, respective cAMP levels were 424 and 449 fmol/(mg/mL), respectively (p = 0.94).

CONCLUSION

Nasal saline irrigation has no subjective or objective effect on olfaction. It also does not appear to affect cAMP levels, a potential marker of smell function.