Olfactory training for COVID-19 related smell loss

The Effect of Olfactory Training in Patients With COVID-19 Induced Olfactory Dysfunction - A Randomized Placebo-controlled Clinical Trial

Not applicable Interventional Rigshospitalet, Denmark · NCT05539560

This study is testing if using essential oils can help people who lost their sense of smell due to COVID-19 get it back better than using fragrance-free oils.

Quick facts

PhaseNot applicable
Study typeInterventional
Enrollment65 (estimated)
Ages18 Years and up
SexAll
SponsorRigshospitalet, Denmark Academic / other
Locations1 site (Copenhagen)
Trial IDNCT05539560 on ClinicalTrials.gov

What this trial studies

This clinical trial investigates the effects of olfactory training using essential oils compared to a placebo in patients experiencing olfactory dysfunction due to COVID-19. Participants will be randomly assigned to either the intervention group, which will use four essential oils (orange, lavender, clove, and peppermint), or the control group, which will use fragrance-free oils. Both groups will engage in a daily olfactory training routine for three months, with their progress monitored through a diary. The study aims to determine if olfactory training can improve the sense of smell in affected individuals.

Who should consider this trial

Good fit: Ideal candidates are adults over 18 years old with olfactory dysfunction specifically caused by COVID-19.

Not a fit: Patients whose olfactory dysfunction is due to causes other than COVID-19 will not benefit from this study.

Why it matters

Potential benefit: If successful, this approach could significantly improve the quality of life for patients suffering from smell loss due to COVID-19.

How similar studies have performed: While olfactory training has been explored in other contexts, this specific approach for COVID-19 related dysfunction is relatively novel.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Olfactory dysfunction caused by COVID-19
* Hyposmia (16.25-30.5) or anosmia (\<16) with or without parosmia assessed by TDI test with Sniffin Sticks performed in the Unit for Sense of Taste and Smell
* \> 18 years of age

Exclusion Criteria:

* Cause of hyposmia, anosmia or parosmia other than COVID-19
* Does not read or speak Danish
* Lack of compliance to perform daily olfactory training

Where this trial is running

Copenhagen

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions COVID-19Olfactory trainingQuality of lifeOlfactory dysfunctionCovid-19Parosmia
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.