The aim of this study was to investigate the response, acute effects and time-course of sensitization and desensitization to allyl isothiocyanate (mustard oil) nasal stimuli in healthy subjects. Sixty subjects participated in the experiment, which employed psychophysical (intensity ratings) and psychophysiological (skin conductance response) measurements. Nasal stimuli were delivered three times with different inter-stimulus intervals. The results showed that the psychophysical and psycho-physiological data were correlated and that the successive nasal stimuli after a short period of time (<2 min) produced increased intensity of irritation, whereas the stimuli delivered after >3 min produced a markedly decreased intensity of irritation. These findings are in agreement with those obtained with capsaicin, the most frequently used irritant molecule.