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For further information, see CMDT Part 8-12: Olfactory Dysfunction

Key Features

Essentials of Diagnosis

  • Subjective diminished smell or taste sensation

  • Lack of objective nasal obstruction

  • Objective decrease in olfaction demonstrated by testing

General Considerations

  • Causes include

    • Anatomic blockage of the nasal cavity with subsequent airflow disruption (hyposmia or anosmia)

    • Polyps

    • Septal deformities

    • Nasal tumors

    • SARS-CoV-2 viral infection (COVID-19 illness)

    • Head trauma (rare but severe cause)

    • Shearing of the olfactory neurites

      • Accounts for < 5% of cases of hyposmia

      • More commonly associated with anosmia

  • Transient olfactory dysfunction often accompanies the common cold, nasal allergies, and perennial rhinitis

  • About 20% of olfactory dysfunction is idiopathic, although it often follows a viral illness

  • Central nervous system neoplasms, especially those that involve the olfactory groove or temporal lobe, may affect olfaction and should be considered in patients with no other explanation for their hyposmia

  • Absent, diminished, or distorted smell or taste has been reported in a wide variety of endocrine, nutritional, and nervous disorders

Clinical Findings

  • Hyposmia and anosmia are cardinal early manifestations of COVID-19

  • Nasal obstruction (from polyps, trauma, foreign bodies, or nasal masses)

    • Can cause functional hyposmia

    • Should be excluded before concluding that the disruption of olfaction is idiopathic


  • In current pandemic, oropharyngeal or nasal swab PCR testing for SARS-CoV-2 virus (cause of COVID-19 illness) should be done

  • The University of Pennsylvania Smell Identification Test (UPSIT)

    • A simple, self-administered "scratch-and-sniff" test that is useful in differentiating hyposmia, anosmia, and malingering

    • Available commercially

  • Odor threshold can be tested at regional specialty centers using increasing concentrations of various odorants


  • Surgically removing the anatomic blockage may be beneficial when olfactory dysfunction is secondary to nasal polyposis, obstruction, and chronic rhinosinusitis

  • Unfortunately, there is no specific treatment for primary disruption of olfaction or for olfactory disorder due to SARS-CoV-2 viral infection



  • The degree of olfactory dysfunction is the greatest predictor of recovery, with less severe olfactory dysfunction recovering at a much higher rate; some cases spontaneously resolve

  • The olfactory symptoms of COVID-19 may linger and even be permanent sequelae

  • In permanent olfactory dysfunction, counseling should be offered about

    • Seasoning foods (such as using pepper that stimulates the trigeminal as well as olfactory chemoreceptors, rather than table salt)

    • Safety issues (such as installing home smoke alarms and using electric rather than gas appliances)


Karimi-Galougahi  M  et al. Anosmia and the need for COVID-19 screening during the pandemic. Otolaryngol Head Neck Surg. 2020;163:96.
[PubMed: 32366195]  
Kasiri  H  et al. Mometasone furoate nasal spray in the treatment of patients with COVID-19 olfactory dysfunction: a randomized, double blind clinical trial. ...

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