Improving smell function in long COVID patients through training and stimulation

A Randomized Controlled Trial of Smell Training and Trigeminal Nerve Stimulation in the Treatment of COVID-related Persistent Smell Loss

PHASE2; PHASE3 · Medical University of South Carolina · NCT05855369

This study is testing two at-home treatments to see if they can help people with long COVID regain their sense of smell and possibly improve other symptoms.

Quick facts

PhasePHASE2; PHASE3
Study typeInterventional
Enrollment145 (estimated)
Ages18 Years to 65 Years
SexAll
SponsorMedical University of South Carolina (other)
Locations1 site (Charleston, South Carolina)
Trial IDNCT05855369 on ClinicalTrials.gov

What this trial studies

This study investigates the effectiveness of two at-home treatments for persistent smell loss associated with long COVID: smell training and non-invasive trigeminal nerve stimulation. Participants will engage in daily treatment sessions over 12 weeks, attend three in-person visits, and complete electronic questionnaires to assess their progress. The goal is to enhance the recovery of olfactory function, which may also alleviate other long COVID symptoms such as mood and cognitive impairments. The study aims to provide valuable insights into the treatment of smell dysfunction in long COVID patients.

Who should consider this trial

Good fit: Ideal candidates are individuals experiencing persistent smell loss after a COVID-19 infection who have not previously undergone smell training or trigeminal nerve stimulation.

Not a fit: Patients with a history of head injuries, sinonasal conditions, neurological disorders, or serious mental illnesses may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could significantly improve the sense of smell for patients suffering from long COVID-related smell loss.

How similar studies have performed: While smell training is being explored as a treatment for COVID-related smell loss, the combination of this with trigeminal nerve stimulation is a novel approach that has not been extensively tested.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* treatment-seeking for COVID-related persistent SL (anosmia, hyposmia, phantosmia or parosmia)
* at least 1-month from SARS-coV-2 PCR-positive and/or rapid home-positive tests
* normal sense of smell prior to COVID
* naïve to both smell training (ST) and trigeminal nerve stimulation (TNS)
* able to comprehend English and provide informed consent

Exclusion Criteria:

* history of head injury (e.g. sport, accident, combat blast)
* sinonasal condition (e.g. upper respiratory infection, rhinosinusitis, polyps)
* neurological disorder (e.g. epilepsy, neurodegenerative disorder, narcolepsy)
* serious mental illness (e.g. schizophrenia, bipolar, or other psychotic disorder)
* suicidal ideation within the last month
* current (≤6 months) heavy cigarette smoker (heavy defined as ≥ 10 pack-years)
* oral/nasal steroids or other intranasal medications within the last month
* immunomodulatory medications
* pregnant or trying to become pregnant

Where this trial is running

Charleston, South Carolina

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.

View on ClinicalTrials.gov →

Conditions: Smell Dysfunction, Olfactory Disorder, Long COVID, COVID-19, Parosmia, Hyposmia, Anosmia, Phantosmia

Last reviewed 2026-05-15 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.