The term anosmia derives from the Greek an (without) and osme (odor); it refers to the absence or impairment of the sense of smell. Hyposmia refers to diminished olfactory functioning. Synonyms for this condition include anosmia, anosphrasia, and olfactory anesthesia. Organic forms of anosmia are categorized as afferent (related to impaired conductivity of the olfactory nerve), central (due to cerebral disease), obstructive (related to obstruction of the nasal fossa), and peripheral (due to diseases of peripheral olfactory nerves).

The most common cause of anosmia is a several head cold or respiratory infection, which intranasal swelling blocks the nasal passages, preventing odors from reaching the olfactory region. This type of anosmia is temporary. Other organic causes of this condition include neoplasms (tumors), head injuries, or chronic rhinitis associated with granulomatous disease.

Anosmia also is a characteristic of olfactogenital dysplasia, also known as Kallman’s syndrome or anosmia eunuchoidism. This condition, more prevalent in males, is associated with lack of development of secondary sexual characterized and anosmia.

The apparently X-linked autosomal dominant or recessive inheritable condition is associated with dysfunction of the hypothalamus and the pituitary. Anosmia with these etiologies typically is a permanent condition. Decreased sense of smell, microsmia, is also common with aging and among smokers.

Psychological forms of anosmia, while less common, may occur. Phobias or fears have been identified as precipitating such forms of anosmia. Specific types of anosmia include anosmia gustatoria (loss of the ability to smell foods) and preferential anosmia (loss of the ability to smell certain odors), provides a detailed description of conditions associated with a disturbance of olfaction and excellent clinical analyses with children.

Anosmia Causes

  • A. Allergic and vasomotor rhinitis
  • N. Nasal obstruction: deviated nasal septum
  • O. Olfactory nerve affections
  • S. Sub-arachnoid hemorrhage
  • M. Meningitis and neurosyphilis
  • I. Idiopathic

Intracranial lesions e.g. absences, tumor, infection, etc.

  • A. atrophic rhinitis

Differential Diagnosis

Head or facial trauma

  • Probably the second common cause of anosmia
  • May result in permanent anosmia
  • CNS rhinorrhea may occur

Post upper respiratory viral infection

  • Accounts for 20%-30% of causes of anosmia

Nasal and sinus disease

  • The most common cause of anosmia
  • Allergic or vasomotor rhinitis and sinusitis result in temporary anosmia.
  • Intranasal polyps may result in obstruction of nasal passages with temporary anosmia.


  • Amphetamines
  • Certain antibiotics (e.g., amikacin, doxycycline, amoxicillin, clarithromycin)
  • Nasal steroids
  • Antithyroid agents
  • Radiation


  • Chemical pollutants
  • Heavy metals (e.g., lead)
  • Volatile organic compounds
  • Inorganic compounds (e.g., vanadium, chromates, cadmium)

Iiicit drugs

  • Intranasal cocaine

Granulomatous disease with destruction of the olfactory nerve

  • Wegener’s granulomatosis
  • Sarcoidosis

CNS disorders

  • Alzheimer’s disease
  • Parkinson’s disease
  • Anxiety disorders


  • Meningioma of the olfactory groove
  • Nasal cavity tumors
  • Brain tumors

Endocrine disorders

  • Diabetes mellitus
  • Hypothyroidism
  • Adrenal insufficiency

Congenial disorders

  • Kallman’s syndrome
  • Turner’s syndrome

Vitamin deficiencies

  • Malnutrition
  • Vitamin B12 deficiency (pernicious anemia)
  • Niacin deficiency (pellagra)
  • Zinc deficiency

Diagnostic Workup & Initial Management

History and physical examination

  • Assess onset and duration, associated symptoms (e.g., allergic symptoms), recent head trauma, exposure (particularly to intranasal zinc), medications, and past medical and surgical history.

°    Rhinitis and sinusitis may be associated with chronic nasal congestion, rhinorrhea, postnasal drip, pale or boggy nasal mucosa, sinus swelling and tenderness, and headaches.

°   Upper or lower respiratory symptoms and renal involvement suggest Wegner’s granulomatosis.

  • Include a complete head and neck exam and a full neurologic exam.

°   Enlarged nasal turbinates suggest sinusitis (turbinates are pale and boggy in chronic allergic sinusitis and erythematous in non-allergic sinusitis)

°      Assess for septal disease (midline granulomas) and polyps

Initial diagnostic workup

  • Several types of smell tests are available:

–      Olfactory threshold and odor identification test

–      University of Pennsylvania scratch and sniff test

–      Alcohol sniff test

  • Initial laboratory testing may include CBC, electrolyte, glucose, BUN and creatinine, calcium, ESR, thyroid profile, liver function tests, and vitamin B12level.
  • Blood and/or urine toxicology screen if suspect drug use or poisoning.
  • Nasal discharge testing for ?-transferrin in CSF
  • Head CT may be indicated to evaluate skull base, brain, nasal cavity, and sinuses.
  • MRI may be indicated to evaluate brain and soft facial tissues.
  • Antibodies to Ro/SSA and LA/SSB are positive in Sjogren’s syndrome.