IRCT20210202050231N1.

Study name	Comparison of the effect of vanilla essential oil with eucalyptus essential oil on the return of olfactory sense in COVID‐19 patients
Methods	Parallel‐group, randomised, controlled, double‐blind trial
Participants	Individuals with a positive PCR test and olfactory impairment Inclusion criteria: Informed consent Positive PCR test No loss of sense of smell/taste in the 2 weeks preceding COVID‐19 infection Non‐smoker Living in the city 18 years and over Exclusion criteria: People with certain underlying conditions (such as asthma and history of allergies, Parkinson's, Alzheimer's, severe eating disorders, acute rhinitis, acute sinusitis, nasal congestion, previous rhinoplasty, traumatic nerve damage, having other viral/bacterial infections at the same time as COVID‐19) People who deal with 'thick' odours in their job, such as working with paint or acid Planned sample size: 84 participants
Interventions	Intervention: Olfactory stimulation for 1 week with either vanilla or eucalyptus scents, using 2.5 mL of 100% pure essential oil to be inhaled every day, 6 times per day after washing the nose with 0.9% saline Comparator: Placebo (no further details given)
Outcomes	Outcomes of interest in the review: Primary outcomes: Presence of normal sense of smell UPSIT will be used to assess olfaction; unclear whether this will be reported as 'recovery' or only as change in score Serious adverse effects Not reported Change in sense of smell Assessed with UPSIT, at 1 and 2 weeks follow‐up Secondary outcomes: Prevalence of parosmia Not reported Change in sense of taste Not reported Disease‐related quality of life Not reported Other adverse effects (including nosebleeds/bloody discharge) Not reported Other outcomes reported by the study: None reported
Starting date	30 April 2021
Contact information	Mohamad Ali Yadegary Email: ma.yadegary@gmail.com
Notes	Trial registered in Iran Estimated recruitment end date: 21 August 2021  It is unclear if participants will have had symptoms for < 4 weeks at baseline, therefore this study may not be suitable for inclusion in this review. Further details will be obtained when the trial is published.