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Completed

NCT Number: NCT06142565

Treatment of Postviral Olfactory Dysfunction

A decreased sense of smell (hyposmia) is often caused by viral infections, such as COVID-19. Today, the only recommended treatment for hyposmia is olfactory training, a time consuming method with limitations in terms of both compliance and effect. The aim of this study is therefore to evaluate, as well as optimize, a new treatment method for olfactory loss.

Hyposmic participants will be recruited and randomized into two different treatment conditions. One group will do regular olfactory training and the other will do passive olfactory training with scented nose plugs. The training will be conducted in the home of the individual monday through friday for two consecutive months. Subjective and objectvie measures of olfactory problems will be assessed before and after treatment, as well as subjective measures related to quality of live and genereal wellbeing.

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Key information

Conditions

Hyposmia Anosmia Nervous System Diseases Neurologic Manifestations Olfaction Disorders Pathological Conditions, Signs and Symptoms Sensation Disorders Signs and Symptoms

Age range

18 year–65 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Karolinska Institutet

Solna, Stockholm County, 17177, Sweden

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • 18 - 65 years old
  • Physically and cognitively capable of participating in the study
  • Having appropriate olfactory screening test scores (hyposmic)

Exclusion criteria

  • Anosmics
  • Individuals with other diagnoses that could affect the study results

Treatment and study plan

Nose plug

Device

Participants will complete olfactory training with scented nose plugs.

Regular olfactory training

Other

Participants will complete olfactory training with regular odors found in their home.

Primary outcomes

  1. Objective olfactory function

    Time frame: 2 months

    Does the use of scented nose plugs increase the effect of olfactory training on objective olfactory function compared to regular olfactory training? For this outcome, we will use the standardized Sniffin' Sticks test to assess olfactory function.

  2. Subjective symptoms and social/emotional consequences

    Time frame: 2 months

    Does the use of scented nose plugs increase the effect of olfactory training on subjective symptoms and social/emotional consequences compared to regular olfactory training? For this outcome, we will use the Sino-Nasal Outcome Test (SNOT).

  3. Subjective health

    Time frame: 2 months

    Does the use of scented nose plugs increase the effect of olfactory training on subjective health compared to regular olfactory training? For this outcome, we will use the Self-Rated Health 5 measure and SF-36.

  4. Subjective olfactory function

    Time frame: 2 months

    Does the use of scented nose plugs increase the effect of olfactory training on subjective olfactory function compared to regular olfactory training? For this outcome, we will use the Self-Reported Mini Olfactory Questionnaire.

  5. Subjective degree of suffering from olfactory impairment

    Time frame: 2 months

    Does the use of scented nose plugs increase the effect of olfactory training on subjective degree of suffering from olfactory impairment compared to regular olfactory training? For this outcome, we will use the Questionnaire of Olfactory Disorders - Negative Statements.

  6. Subjective parosmia

    Time frame: 2 months

    Does the use of scented nose plugs increase the effect of olfactory training on subjective parosmia compared to regular olfactory training? For this outcome, we will use the Landis parosmia questionnaire.

  7. Subjective depressive symptoms

    Time frame: 2 months

    Does the use of scented nose plugs increase the effect of olfactory training on depressive symptoms compared to regular olfactory training? For this outcome, we will use the Beck Depression Inventory (BDI).

  8. Subjective general wellbeing

    Time frame: 2 months

    Does the use of scented nose plugs increase the effect of olfactory training on depressive symptoms compared to regular olfactory training? For this outcome, we will use the General Well Being Schedule.

  9. Compliance

    Time frame: 2 months

    Does the use of scented nose plugs increase the compliance of olfactory training compared to regular olfactory training? For this outcome, we will use questions asking the participants about their experience during the olfactory training, specifically targeting their compliance, such as how often they actually completed the olfactory training and how often they forgot to.

Sponsors and collaborators

Lead sponsor

Karolinska Institutet

Other

Collaborators

  • Region Skane

Registry information

Important dates

Study start
2023
Primary completion
2024
Study completion
2025
First posted
Nov 21, 2023
Registry last updated
Sep 3, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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