UMIN000043537.

Study name	Post COVID‐19 anosmia
Methods	4‐arm, double‐blind, parallel‐group RCT. Duration of treatment and follow‐up unclear.
Participants	Adults with olfactory dysfunction following COVID‐19 Inclusion criteria: Aged 40 to 65 years Post‐COVID‐19 smell dysfunction (no further details) Exclusion criteria: Current use of nasal or systemic steroids Previous chronic rhinological pathology Anosmia that had improved before recovery from COVID‐19 Pregnant women Those who did not complete follow‐up Estimated sample size: 200 participants
Interventions	Intervention A Combination of local corticosteroid and antihistamine nasal spray Intervention B Local corticosteroid nasal spray Intervention C Antihistamine nasal spray Comparator: Normal saline nasal spray 0.2%  No further details provided on any of the interventions or comparator
Outcomes	Outcomes of interest in the review: Primary outcomes: Presence of normal olfactory function Butanol threshold test and discrimination test. Unclear if this will be reported as a dichotomous or continuous outcome. Serious adverse effects Not reported Change in sense of smell Butanol threshold test and discrimination test. Unclear if this will be reported as a dichotomous or continuous outcome. 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	1 January 2021
Contact information	Asmaa Salah Mohamed  Email: asmaa.elsadorry@yahoo.com
Notes	Registered in Egypt. Trial end date not reported.  It is unclear if participants will have had symptoms for < 4 weeks at baseline, therefore this trial may not be suitable for inclusion in this review. Further details will be obtained when the trial is published.