NCT05855369 · Medical University of South Carolina
Study of Chemosensory Enhancement Through Neuromodulation Training (SCENT for Long COVID)
What this study is about
Persistent smell loss that can include diminished or distorted smell function is a common symptom of long COVID syndrome. There are limited treatment options for long COVID-related smell loss. This study aims to determine the effectiveness of two at-home treatments, smell training and non-invasive trigeminal nerve stimulation.
View original scientific description
Persistent smell loss that can include diminished or distorted smell function is a common symptom of long COVID syndrome. There are limited treatment options for long COVID-related smell loss. This study aims to determine the efficacy of two at-home treatments, smell training and non-invasive trigeminal nerve stimulation. This study requires participants to conduct daily at-home treatment sessions, attend three in-person study visits at the MUSC Department of Psychiatry and Behavioral Sciences, and complete electronic questionnaires over the 12-week trial, and again at the six-month timepoint. Participants in this trial may benefit directly with an improvement in sense of smell. However, participation may also help society more generally, as this study will provide new information about long COVID-related smell loss and its treatment.
Interventions
DEVICE
Trigeminal Nerve Stimulation (TNS)
Non-invasive, pain-free, low-level electrical stimulation to the forehead to modulate the trigeminal nerve and enhance smell function through activation of the highly connected olfactory-intranasal trigeminal brain circuits.
OTHER
Active Smell Training (ST)
Sniffing various higher intensity odorant chemicals while performing odor-related cognitive tasks. 16 odorant chemicals will be used for training including: 2 phenyl ethanol, eugenol, lemon, eucalyptus, cinnamon, peppermint, coffee, mandarin, lavender, vanilla, lilac, ginger, chocolate, thyme, banana, and bacon.
OTHER
Placebo Smell Training (PBO)
Sniffing the same lower intensity odorant chemicals (i.e. N-butanol and 2-phenyl ethanol) over the course of the trial and performing no odor-related cognitive tasks.
Primary outcome measures
Change in Psychophysical Olfactory Function from Baseline to 4 and 12 Weeks
Time frame: 2 times: 4 weeks, 12 weeks
Sniffin' Sticks (Bughardt Messtechnik, Wedel Germany) will be used to determine odor threshold (T), odor discrimination (D), and odor identification (I), each on 16-point scales, and summed for a total TDI score. Higher scores indicate better function.
Change in Perceived Intensity of Odorants from Baseline to 4 and 12 Weeks
Time frame: 2 times: 4 weeks, 12 weeks
Perceived intensity on 100-mm visual analog scales with anchor points: 0="imperceptible" to 100="extremely intense" will be rated for suprathreshold concentrations of PEA, vanilla, eugenol, and eucalyptus.
Change in Perceived Hedonics of Odorants from Baseline to 4 and 12 Weeks
Time frame: 2 times: 4 weeks, 12 weeks
Perceived hedonics on 100-mm visual analog scales with anchor points: 0="extremely unpleasant" to 100="extremely pleasant".
Change in Olfactory-related Quality of Life from Baseline to 4 and 12 Weeks
Time frame: 2 times: 4 weeks, 12 weeks
The Modified Questionnaire of Olfactory Disorders-Negative Statements (QOD-NS) consists of 17 negative statements (rated on a scale from 0 to 3; total score ranging from 0 to 51), with lower scores indicating better olfactory-related quality of life.
Change in Impact of Olfactory Loss from Baseline to 4 and 12 Weeks
Time frame: 2 times: 4 weeks, 12 weeks
The Impact of Olfactory Loss Visual Analog Scale (IOL-VAS) consists of 9 separate items assessing the impact of olfactory loss upon mood, food enjoyment, social interactions, safety, hygiene, sex, cooking, appetite, and weight changes, rated from 0 (no impact) to 10 (biggest impact possible).
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
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
- Charleston, South Carolina
Collaborators
National Institutes of Health (NIH), National Institute on Deafness and Other Communication Disorders (NIDCD)
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Apr 2, 2026 · Source of record for eligibility and locations