* Causes of olfactory dysfunction can be classified into conductive and sensorineural causes. * Conductive causes are mainly due to structural nasal problem, which can be treated by nasal surgery * Sensorineural causes included post-infection, post-head injury, post Head and Neck irradiation and other central nervous system diseases. * Olfactory Training is well established treatment for sensorineural olfactory dysfunction in foreign countries. * Olfactory Training by neurological chemosensory stimulation using aromatic substances delivered via electronic portable aromatic rehabilitation (EPAR) diffuser was proved to be effective treatment in COVID-19 related olfactory dysfunction in recent Hong Kong study. * However, there is a lack of local study on the effect of Olfactory Training in other non-COVID-19 sensorineural causes of olfactory dysfunction in Hong Kong population.
Olfactory dysfunction > 6 months and < 5 years
History of significant head injury (fracture, ICH)
History of brain surgery
History of nasal surgery
Active nasal disease
Parallel
Olfactory Training
Other interventionFour aromatic substances will be used (Citrus limon, Eucalyptus radiata, Pelargonium graveolens, Juniperus virginiana)
Control
Other interventionNormal Saline will be used
Olfactory threshold changes after olfactory training after 3 months
Parameter: Olfactory threshold using Butanol Threshold Test (BTT)
Olfactory identification score changes after olfactory training after 3 months
Parameter: Olfactory identification using Smell Identification Test (UPSIT)
Quality of life changes after olfactory training after 3 months
Parameter: Subjective quality of life score using Sino-Nasal Outcome Test (SNOT-22)
Taste and smell changes after olfactory training after 3 months
Parameter: Subjective smell and taste assessment using Visual Analogue Scale (VAS)
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