Various nasal humidifying agents are being promoted for regular use. In this study we compared the effects of three formulations (medium 199, 0.9% saline and a commercially available isotonic sea-water formulation -- Rhinomer) on ciliary beat frequency using rat tracheal cilia as a model. Surface response methodology was used to evaluate the effects of pH and osmolality of the formulation on ciliotoxicity. Our results showed that none of the formulations differed in their effects on cilia. Moreover, neither medium 199 nor Rhinomer protected the cilia from the effects of drugs (chlorbutol, xylometazoline, azelastine and lignocaine) known to be ciliotoxic.