Effects of Isotretinoin on Smell

May 2, 2026 updated by: Uşak University

Effects of Isotretinoin on Nasal Mucociliary Clearance and Olfactory Function

Isotretinoin is a common medicine used to treat moderate to severe acne. It often causes dryness of the skin and the inside of the nose. Because a normal sense of smell depends on a healthy nasal lining, this dryness may affect how well a person can smell.

This study will examine whether isotretinoin treatment changes the sense of smell in adults with acne. Before starting isotretinoin, participants will complete a standardized smell test and two short questionnaires about nasal symptoms and quality of life: the Nasal Obstruction Symptom Evaluation (NOSE) scale and the 22-item Sino-Nasal Outcome Test (SNOT-22). After at least 4 weeks of treatment, the same smell test and questionnaires will be repeated.

By comparing results before and after treatment, the study will test the hypothesis that isotretinoin has a negative effect on olfactory function and may reduce patients' ability to smell.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

Isotretinoin is a systemic retinoid widely used for the treatment of moderate to severe acne that does not respond adequately to conventional topical or oral therapies. Although highly effective, isotretinoin is known to cause mucocutaneous dryness, which may alter the nasal environment and potentially influence olfactory function. The sense of smell depends on the integrity of the olfactory epithelium, the moisture of the nasal mucosa, and the ability of odorant molecules to reach and dissolve within the mucus layer. Changes in these factors may lead to measurable reductions in olfactory sensitivity or identification ability.

Previous studies examining the effects of isotretinoin on olfaction have produced conflicting results. One investigation reported an increase in olfactory sensitivity during treatment, while another found a decrease in smell function using a different testing method. These inconsistent findings, combined with the limited number of available studies, highlight the need for further research using standardized and reproducible assessment tools.

This prospective clinical study will evaluate olfactory function in adults initiating isotretinoin therapy for dermatologic indications. Participants will undergo a structured olfactory assessment using the Connecticut Chemosensory Clinical Research Center (CCCRC) smell test, which includes both odor identification and discrimination components. In parallel, patient-reported nasal symptoms and sinonasal-related quality of life will be assessed using the NOSE and SNOT-22 questionnaires, allowing a broader understanding of subjective nasal changes that may accompany isotretinoin use.

All assessments will be performed at two time points: before the start of isotretinoin therapy and after a minimum of four weeks of continuous treatment. This within-subject design will allow comparison of pre-treatment and post-treatment measurements to determine whether isotretinoin produces quantifiable changes in olfactory performance. The study hypothesis is that isotretinoin may negatively affect olfactory function due to its well-recognized drying effects on the nasal mucosa.

The findings of this research may assist clinicians in counseling patients regarding potential sensory side effects of isotretinoin and may provide a basis for further investigations into the mechanisms by which systemic medications influence nasal physiology and smell perception.

Study Type

Interventional

Enrollment (Estimated)

54

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Diagnosed with acne and scheduled to start oral isotretinoin as part of routine dermatology care
  • Willing to participate and able to give informed consent
  • Not currently smoking
  • No history of allergic rhinitis, sinusitis, or active upper respiratory infection
  • No medical condition known to affect the sense of smell

Exclusion Criteria:

  • Younger than 18 years or older than 45 years
  • Current cigarette smoking
  • History of chronic sinonasal disease
  • Any condition that would prevent completing the smell test
  • Not willing to continue participation or withdrawal of consent at any time

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Isotretinoin Treatment Group
Participants in this arm will receive standard-of-care oral isotretinoin prescribed by the Dermatology Department for the treatment of acne vulgaris. The dosage and duration of isotretinoin therapy will follow routine clinical practice and will be determined by the treating dermatologist. Olfactory function and nasal symptom assessments will be performed before starting isotretinoin and after at least four weeks of treatment.
Drug: isotretinoin
Oral isotretinoin prescribed as standard-of-care treatment for acne vulgaris. The dosage, formulation, and duration of therapy will follow routine clinical practice and will be determined by the treating dermatologist based on the participant's clinical condition and body weight. Participants will typically receive daily oral isotretinoin for at least four weeks before the post-treatment assessments.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change in Olfactory Function Score
Time Frame: Baseline and 4 weeks after starting isotretinoin treatment.
Change in olfactory function from baseline to at least 4 weeks after initiation of oral isotretinoin therapy, measured using the Connecticut Chemosensory Clinical Research Center (CCCRC) smell test. The CCCRC test includes odor identification and odor discrimination components, and yields a composite score representing overall olfactory performance.
Baseline and 4 weeks after starting isotretinoin treatment.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Uşak University

Collaborators

The Scientific and Technological Research Council of Turkey

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

June 1, 2025

Primary Completion (Estimated)

June 1, 2026

Study Completion (Estimated)

June 1, 2026

Study Registration Dates

First Submitted

December 15, 2025

First Submitted That Met QC Criteria

December 15, 2025

First Posted (Actual)

December 30, 2025

Study Record Updates

Last Update Posted (Actual)

May 7, 2026

Last Update Submitted That Met QC Criteria

May 2, 2026

Last Verified

December 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • ISO51116
  • 1919B012412359 (Other Grant/Funding Number: This study was supported by the Scientific and Technological Research Council of Turkey (TÜBİTAK).)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data will not be shared because institutional policy does not permit external sharing of health-related data.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Smell Dysfunction

Clinical Trials on isotretinoin

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

CROs by country

CROs in Djibouti

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Subscribe