Smell and Taste Disorders
- Physiologically, the senses of smell and taste aid in normal digestion by triggering GI secretions.
- 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
There are ~200,000 patient visits a year for smell and taste disturbances.
- Predominant sex: male > female. Men begin to lose their ability to smell earlier in life than women.
- Predominant age:
- 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:
- COVID-19—common in mildly symptomatic patients (~65%) but even more common in patients needing hospitalization (85%) (1),(2),(3). While most recovery occurs within a few weeks, 7% of chemosensory disorders persist beyond 60 days (3). Unexplained chemosensory loss is a good predictor of COVID-19 (4),(5)[B].
- Nutritional factors (e.g., malnutrition, vitamin deficiencies, liver disease, pernicious anemia)
- Endocrine disorders (e.g., thyroid disease, diabetes mellitus, renal disease)
- Migraine headache (e.g., gustatory aura, olfactory aura)
- Sjögren syndrome
- Toxic exposures
- Neurodegenerative diseases (e.g., multiple sclerosis, Alzheimer disease, cerebrovascular accident, Parkinson disease)
- Smell-specific disturbance:
- Nasal and sinus disease (e.g., allergies, rhinitis, rhinorrhea, URI)
- Cigarette smoking
- Cocaine abuse (intranasal)
- Neoplasm (e.g., brain tumor, nasal polyps, intranasal tumor)
- Systemic lupus erythematosus (SLE)
- Bell palsy
- Taste-specific loss:
- Oral appliances, procedures
- Intraoral abscess, gingivitis
- Damage to CN VI, IX, or X
- Stroke (especially frontal lobe)
- Selected medications:
- 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
- Poor nutritional status
- Well-balanced diet
- Maintain good oral and nasal health.
- Avoid tobacco products, chemical exposures.
Anosmia also may be an early sign of degenerative disorders and has been shown to predict increased 5-year mortality (6)[B].
- 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).
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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Domino, Frank J., et al., editors. "Smell and Taste Disorders." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2020. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116561/all/Smell_and_Taste_Disorders.
Smell and Taste Disorders. In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2020. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116561/all/Smell_and_Taste_Disorders. Accessed May 29, 2023.
Smell and Taste Disorders. (2020). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (27th ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116561/all/Smell_and_Taste_Disorders
Smell and Taste Disorders [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2020. [cited 2023 May 29]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116561/all/Smell_and_Taste_Disorders.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Smell and Taste Disorders ID - 116561 ED - Domino,Frank J, ED - Baldor,Robert A, 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 -