Anosmia

Anosmia
Other names	Loss of smell, smell blindness,[1] odor blindness
Inflamed nasal mucosa causing anosmia
Pronunciation	/ænˈɒzmiə/
Specialty	Otorhinolaryngology
Types	Partial, total[2]

Anosmia, also known as smell blindness, is the loss of the ability to detect one or more smells.^[1][2] Anosmia may be temporary or permanent.^[3] It differs from hyposmia, which is a decreased sensitivity to some or all smells.^[2]

Anosmia can be due to a number of factors, including

When anosmia is caused by inflammatory changes in the nasal passageways, it is treated simply by reducing inflammation.[7]^[8] It can be caused by chronic meningitis and neurosyphilis that would increase intracranial pressure over a long period of time,^[9] and, in some cases, by ciliopathy,^[10] including ciliopathy due to primary ciliary dyskinesia.^[11]

The term derives from the

In the United States, 3% of people aged over 40 are affected by anosmia.[3]

Anosmia is a common symptom of COVID-19 and can persist as long COVID.^[13]

Definition

Anosmia is the inability to smell.^[1] It may be partial or total, and can be specific to certain smells.^[2] Reduced sensitivity to some or all smells is hyposmia.^[2]

Signs and symptoms

Anosmia can have a number of harmful effects.

Many experience one sided loss of smell, often as a result of minor head trauma. This type of anosmia is normally only detected if both of the nostrils are tested separately. Using this method of testing each nostril separately will often show a reduced or even completely absent sense of smell in either one nostril or both, something which is often not revealed if both nostrils are simultaneously tested.[15]

Losing an established and sentimental

Loss of the ability to smell may lead to the loss of libido, but this usually does not apply to those with olfactory dysfunction at birth.^[16][17]

Often people who have loss of smell at birth report that they pretended to be able to smell as children because they thought that smelling was something that older/mature people could do, or did not understand the concept of smelling but did not want to appear different from others. When children get older, they often realize and report to their parents that they do not actually possess a sense of smell, often to the surprise of their parents.^{[citation needed]}

Causes

A temporary loss of smell can be caused by a blocked nose or infection. In contrast, a permanent loss of smell may be caused by death of olfactory receptor neurons in the nose or by brain injury in which there is damage to the olfactory nerve or damage to brain areas that process smell (see olfactory system). The lack of the sense of smell at birth, usually due to genetic factors, is referred to as congenital anosmia. Family members of the patient with congenital anosmia are often found with similar histories; this suggests that the anosmia may follow an autosomal dominant pattern.^[18] Anosmia may very occasionally be an early sign of a degenerative brain disease such as Parkinson's disease and Alzheimer's disease.^{[citation needed]}

Another specific cause of permanent loss could be from damage to olfactory receptor neurons because of use of certain types of nasal spray; i.e., those that cause vasoconstriction of the nasal microcirculation. To avoid such damage and the subsequent risk of loss of smell, vasoconstricting nasal sprays should be used only when absolutely necessary and then for only a short amount of time. Non-vasoconstricting sprays, such as those used to treat allergy-related congestion, are safe to use for prescribed periods of time.^[19] Anosmia can also be caused by nasal polyps. These polyps are found in people with allergies, histories of sinusitis, and family history. Individuals with cystic fibrosis often develop nasal polyps.^{[citation needed]}

Amiodarone is a drug used in the treatment of arrhythmias of the heart. A clinical study demonstrated that the use of this drug induced anosmia in some patients. Although rare, there was a case in which a 66-year-old male was treated with amiodarone for ventricular tachycardia. After the use of the drug he began experiencing olfactory disturbance, however after decreasing the dosage of amiodarone, the severity of the anosmia decreased accordingly, suggesting a relationship between use of amiodarone to the development of anosmia.^[20]

COVID-19-related anosmia

Chemosensory disturbances, including loss of smell or taste, are the predominant neurological symptom of COVID-19.^[21][22] As many as 80% of COVID-19 patients exhibit some change in chemesthesis, including smell. Loss of smell has also been found to be more predictive of COVID-19 than all other symptoms, including fever, cough or fatigue, based on a survey of 2 million participants in the UK and US.^[23] Google searches for "smell", "loss of smell", "anosmia", and other similar terms increased since the early months of the pandemic, and strongly correlated with increases in daily cases and deaths.^[24] Research into the mechanisms underlying these symptoms is currently ongoing.^[25][26]

Many countries list anosmia as an official COVID-19 symptom, and some have developed "smell tests" as potential screening tools.^[27][28]

In 2020, the Global Consortium for Chemosensory Research, a collaborative research organization of international smell and taste researchers, formed to investigate loss of smell and related chemosensory symptoms.^[29]

Possible causes

Diagnosis

Diagnosis begins with a detailed history, including possible related injuries, such as upper respiratory infections or head injury. The examination may involve nasal endoscopy for obstructive factors such as polyps or swelling.^[4] A nervous system examination is performed to see if the cranial nerves are affected.^[4] On occasion, after head traumas, there are people who have unilateral anosmia. The sense of smell should be tested individually in each nostril.^[15]

Many cases of congenital anosmia remain unreported and undiagnosed. Since the disorder is present from birth the individual may have little or no understanding of the sense of smell, hence is unaware of the deficit.^[51] It may also lead to reduction of appetite.^[52]

Treatment

Though anosmia caused by brain damage cannot be treated, anosmia caused by inflammatory changes in the mucosa may be treated with

Anosmia caused by a nasal polyp may be treated by steroidal treatment or removal of the polyp.^[54]

Although very early in development,

In the United States 3% of people aged over 40 are affected by anosmia.[3]

In 2012, smell was assessed in persons aged 40 years and older with rates of anosmia/severe hyposmia of 0.3% at age 40–49 rising to 14.1% at age 80+. Rates of hyposmia were much higher: 3.7% at age 40–49 and 25.9% at 80+.^[57]

Famous people with anosmia

This section needs expansion. You can help by adding to it. (January 2024)

• Kathy Clugston, British radio presenter^[58][59]
• Ben Cohen of Ben and Jerry's^[60][61]
• Perrie Edwards from Little Mix^[62]
• Lorenzo de' Medici, 15th century ruler of Florence^[63]

See also

• Phantosmia
• Parosmia
• Anosmia Awareness Day
• Zicam, a medicine that caused some users to permanently lose their sense of smell
• Ageusia, the loss of the sense of taste

References

Further reading

Scholia has a profile for anosmia (Q468433).

• Blodgett B (2010). Remembering Smell: A Memoir of Losing—and Discovering—the Primal Sense. Houghton Mifflin Harcourt.
  ISBN 978-0-618-86188-0
  .
• Birnbaum M (2011). Season to Taste: How I Lost my Sense of Smell and Found my Way. Ecco.
  ISBN 978-0-06-191531-4
  .
• DeVere R, Calvert M (2010). Navigating Smell and Taste Disorders. Demos Health.
  ISBN 978-1-932603-96-5
  .
• Gilbert A (2008). What the Nose Knows.The Science of Scent in Everyday Life. Crown.
  ISBN 978-1-4000-8234-6
  .
• Herz R (2007). The Scent of Desire. Discovering Our Enigmatic Sense of Smell. HarperCollins.
  ISBN 978-0-06-082538-6
  .
• Tafalla M (2010). Nunca sabrás a qué huele Bagdad (You will never know the smell of Bagdad) (in Spanish). Autonomous University of Barcelona.
  ISBN 978-84-490-2611-9
  . - Novel dealing with congenital anosmia.
• Keller A, Malaspina D (July 2013). "Hidden consequences of olfactory dysfunction: a patient report series". BMC Ear, Nose and Throat Disorders. 13 (1): 8.
  PMID 23875929
  .
• Tafalla M (September 2013). "A world without the olfactory dimension". Anatomical Record. 296 (9): 1287–1296.
  PMID 23907763
  .
• Tafalla M (2013). "Anosmic Aesthetics". Estetika: The Central European Journal of Aesthetics. 50 (1/2013). Prag: 53–80.
  doi:10.33134/eeja.103
  .
• Wilson DA, Stevenson RJ (2006). Learning to Smell. Olfactory Perception from Neurobiology to Behavior. The Johns Hopkins University Press.
  ISBN 978-0-8018-8368-2
  .