Design Prospective double-blinded randomized control trial.~Study Period 1/7/2022 - 30/6/2024 for case recruitment.~Suitable patient will be recruited. Informed consent will be signed. Objective smell assessment will be done using the University of Pennsylvania Smell Identification Test (UPSIT) and Butanol Threshold Test (BTT). Subjective quality of life score will be obtained by Sino-Nasal Outcome Test (SNOT-22). Subjective smell and taste assessment will be assessed by Visual Analogue Scale (VAS). Patient will be randomized into treatment group and control group using computer generated list by an independent nursing staff. Doctors and the patients will be blinded during the study.
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.