Smell and Taste Disorders

Smell and Taste Disorders is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • The senses of smell and taste allow a full appreciation of the flavor and palatability of foods and also serve as a warning system against toxins, polluted air, smoke, and spoiled food.
  • Physiologically, the chemical senses aid in normal digestion by triggering GI secretions. Smell/taste dysfunction may have a significant impact on quality of life.
  • Loss of smell occurs more frequently than loss of taste, and patients frequently confuse the concepts of flavor loss (as a result of smell impairment) with taste loss (an impaired ability to sense sweet, sour, salty, or bitter).
  • Smell depends on the functioning of CN I (olfactory nerve) and CN V (trigeminal nerve).
  • Taste depends on the functioning of CNs VII, IX, and X. Because of these multiple pathways, total loss of taste (ageusia) is rare.
  • Systems affected: nervous, upper respiratory

Epidemiology

Incidence
There are ~200,000 patient visits a year for smell and taste disturbances.


Prevalence
  • Predominant sex: male > female. Men begin to lose their ability to smell earlier in life than women.
  • Predominant age: Chemosensory loss is age dependent:
    • Age >80 years: 80% have major olfactory impairment; nearly 50% are anosmic.
    • Ages 65 to 80 years: 60% have major olfactory impairment; nearly 25% are anosmic.
    • Age <65 years: 1–2% have smell impairment.
  • Estimated >2 million affected in the United States

Etiology and Pathophysiology

  • Smell and/or taste disturbances:
    • Nutritional factors (e.g., malnutrition, vitamin deficiencies, liver disease, pernicious anemia)
    • Endocrine disorders (e.g., thyroid disease, diabetes mellitus, renal disease)
    • Head trauma
    • Migraine headache (e.g., gustatory aura, olfactory aura)
    • Sjögren syndrome
    • Toxic chemical exposure
    • Industrial agent exposure
    • Aging
    • Medications (see below)
    • Neurodegenerative diseases (e.g., multiple sclerosis, Alzheimer disease, cerebrovascular accident, Parkinson disease)
    • Infections (e.g., upper respiratory infection [URI], oral and perioral infections, candidiasis, coxsackievirus, AIDS, viral hepatitis, herpes simplex virus)
  • Possible causes of smell disturbance:
    • Nasal and sinus disease (e.g., allergies, rhinitis, rhinorrhea, URI)
    • Cigarette smoking
    • Cocaine abuse (intranasal)
    • Hemodialysis
    • Radiation treatment of head and neck
    • Congenital conditions
    • Neoplasm (e.g., brain tumor, nasal polyps, intranasal tumor)
    • Systemic lupus erythematosus (SLE)
    • Bell palsy
    • Oral/perioral skin lesion
    • Damage to CN I/V
    • Possible association with psychosis and schizophrenia
  • Possible causes of taste loss:
    • Oral appliances
    • Dental procedures
    • Intraoral abscess
    • Gingivitis
    • Damage to CN VI, IX, or X
    • Stroke (especially frontal lobe)
  • Selected medications that reportedly alter smell and taste:
    • Antibiotics: amikacin, ampicillin, azithromycin, ciprofloxacin, clarithromycin, doxycycline, griseofulvin, metronidazole, ofloxacin, tetracycline, terbinafine, β-lactamase inhibitors
    • Anticonvulsants: carbamazepine, phenytoin
    • Antidepressants: amitriptyline, doxepin, imipramine, nortriptyline
    • Antihistamines and decongestants: zinc-based cold remedies (Zicam)
    • Antihypertensives and cardiac medications: acetazolamide, amiloride, captopril, diltiazem, hydrochlorothiazide, nifedipine, propranolol, spironolactone
    • Anti-inflammatory agents: auranofin, gold, penicillamine
    • Antimanic drugs: lithium
    • Antineoplastics: cisplatin, doxorubicin, methotrexate, vincristine
    • Antiparkinsonian agents: levodopa, carbidopa
    • Antiseptic: chlorhexidine
    • Antithyroid agents: methimazole, propylthiouracil
    • Lipid-lowering agents: statins

Genetics
May be related to underlying genetically associated diseases (Kallmann syndrome, Alzheimer disease, and other neurodegenerative disorders, migraine syndromes, rheumatologic conditions, endocrine disorders)

Risk Factors

  • Age >65 years
  • Poor nutritional status
  • Smoking tobacco products

General Prevention

  • Eat a well-balanced diet, with appropriate vitamins and minerals.
  • Maintain good oral and nasal health, with routine visits to the dentist.
  • Do not smoke tobacco products.
  • Avoid noxious chemical exposures/unnecessary radiation.
Geriatric Considerations
  • Elders are at particular risk of eating spoiled food or inadvertently being exposed to natural gas leaks owing to anosmia from aging.
  • Anosmia also may be an early sign of degenerative disorders and has been shown to predict increased 5-year mortality (1)[B].
Pediatric Considerations
  • Smell and taste disorders are uncommon in children in developed countries.
  • In developing countries with poor nutrition (particularly zinc depletion), smell and taste disorders may occur.
  • Delayed puberty in association with anosmia (± midline craniofacial abnormalities, deafness, or renal abnormalities) suggests the possibility of Kallmann syndrome (hypogonadotropic hypogonadism).
Pregnancy Considerations
  • Pregnancy is an uncommon cause of smell and taste loss or disturbances.
  • Many women report increased sensitivity to odors during pregnancy as well as an increased dislike for bitterness and a preference for salty substances.

Commonly Associated Conditions

URI, allergic rhinitis, dental abscesses

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Citation

* When formatting your citation, note that all book, journal, and database titles should be italicized* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Smell and Taste Disorders ID - 116561 ED - Baldor,Robert A, ED - Domino,Frank J, ED - Golding,Jeremy, ED - Stephens,Mark B, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116561/all/Smell_and_Taste_Disorders PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -