Population variability in nasal irritant (chemesthesic) sensitivity has been postulated by both clinicians and epidemiologists studying indoor and ambient air pollution. Among experimentalists, however, limited attention has been paid to variance in this trait. Candidate susceptibility markers include age, gender, presence or absence of nasal allergies or olfactory dysfunction, cognitive bias and self-reported pollutant reactivity. For most of these markers, conflicting data exist. This review distinguishes between functional subcomponents of nasal irritant sensitivity (sensory acuity versus physiologic reactivity), catalogs psychophysical and physiological methods for their study and examines the current evidence for variation in this trait. In general, interindividual variability has been an under-studied phenomenon.