Use of olfactory training in post‐traumatic and postinfectious olfactory dysfunction

OBJECTIVES/HYPOTHESIS: There is evidence that the olfactory system can be modulated by repeated exposure to odors, a procedure called olfactory training. The aim of this study was to assess the effectiveness of olfactory training in patients with postinfectious and post-traumatic olfactory dysfunction. STUDY DESIGN: Prospective study of 119 patients with postinfectious and post-traumatic olfactory dysfunction. METHODS: Two groups of patients (postinfectious and post-traumatic) performed the olfactory training (n = 49 and n = 23, respectively) over a period of 16 weeks and were compared with two control groups of the same etiology (n = 32 and n = 15). Patients with sinunasal, neurologic, or idiopathic disease were excluded. Training was performed twice daily with the use of four odors (phenyl ethyl alcohol rose, eucalyptol eucalyptus, citronellal lemon, and eugenol cloves). Olfactory testing was performed by means of the Sniffin' Sticks test battery (threshold, discrimination, identification) at the time of diagnosis, and 8 and 16 weeks later. All patients evaluated their olfactory function by means of a visual analogue scale (0-100). RESULTS: Compared to controls, training patients in both groups presented significantly higher scores of olfactory function as measured by the Sniffin' Sticks test. This increase was measured in 67.8% of postinfectious and 33.2% of post-traumatic patients. Subjective ratings were in accordance with the olfactory test results. Subset analysis showed that olfactory function mainly increased olfactory identification followed by discrimination in both training groups. CONCLUSIONS: The present study suggests that a 16-week short-term exposure to specific odors may increase olfactory sensitivity in patients with postinfectious and post-traumatic olfactory dysfunction.