Additive effect of free-choice olfactory training combined with pharmacotherapy: A retrospective analysis of post-viral olfactory dysfunction.

OBJECTIVE: Post-viral olfactory dysfunction (PVOD) is characterized by a sudden loss of smell following an upper respiratory tract infection. Although various medications, including tokishakuyakusan, zinc sulfate, and vitamin B12, have been used to treat PVOD, their efficacy remains limited. Recently, olfactory training (OT) has been reported to improve sensorineural olfactory loss. This study aimed to evaluate the additive effect of OT combined with conventional pharmacotherapy in patients with PVOD. METHODS: Patients diagnosed with PVOD who visited the smell and taste clinic of a tertiary university hospital between 2008 and 2024 were retrospectively analyzed. Those treated from 2008 to 2014 received tokishakuyakusan, zinc sulfate, and methylcobalamin (medication-alone group), whereas those treated from 2015 to 2024 additionally performed OT (combination group). Cases of olfactory dysfunction resulting from COVID-19 infection between 2020 and 2024 were excluded. Olfactory function was evaluated using the Japanese standard T&T olfactometry, and improvement was assessed according to the criteria of the Japanese Rhinologic Society. RESULTS: A total of 107 patients were included: 65 in the medication-alone group and 42 in the combination group. The combination group showed significantly greater improvement in olfactory function six months after treatment initiation (p = 0.016). Final improvement was achieved in 90% of the combination group and 69% of the medication-alone group (p = 0.010). The mean time to improvement was significantly shorter with combination therapy (8 vs. 14 months, p = 0.001). Multivariate analysis identified OT as an independent factor associated with improvement (p = 0.009; odds ratio, 4.96; 95% CI, 1.50-16.4). CONCLUSION: Combining conventional pharmacotherapy with OT produces an additive effect on olfactory recovery in patients with PVOD, increasing the improvement rate and shortening the recovery period. The free-choice OT protocol, allowing patients to select familiar odorants, represents a simple and practical method suitable for clinical application.