Smell and Taste Disorders
Explore 5-Minute Clinical Consult - view these FREE monographs:
-- The first section of this topic is shown below --
- 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.
- System(s) 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: Chemosensory loss is age-dependent:
- Age >80 years: 80% have major olfactory impairment; nearly 50% are anosmic.
- Ages 65–80 years: 60% have major olfactory impairment; nearly 25% are anosmic.
- Age <65 years: 1–2% have smell impairment.
- Estimated >2 million affected in the US
- Age >65 years
- Poor nutritional status
- Smoking tobacco products
May be related to underlying genetically associated diseases (Kallmann syndrome, Alzheimer disease, migraine syndromes, rheumatologic conditions, endocrine disorders)
- 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.
- 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 such as Alzheimer disease.
- 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 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.
- Smell and/or taste disturbances (1,2):
- Nutritional factors (e.g., malnutrition, vitamin deficiencies, liver disease, 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
- 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)
- Cigarette smoking
- Cocaine abuse (intranasal)
- 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
- Damage to CN VI, IX, or X
- Stroke (especially frontal lobe)
- Selected medications that reportedly alter smell and taste:
- Antibiotics: Amikacin, ampicillin, azithromycin (Zithromax), ciprofloxacin (Cipro), clarithromycin (Biaxin), doxycycline, griseofulvin (Grisactin), metronidazole (Flagyl), ofloxacin (Floxin), tetracycline, terbinafine (Lamisil), β-lactamase inhibitors
- Anticonvulsants: Carbamazepine (Tegretol), phenytoin (Dilantin)
- Antidepressants: Amitriptyline (Elavil), clomipramine (Anafranil), desipramine (Norpramin), doxepin (Sinequan), imipramine (Tofranil), nortriptyline (Pamelor)
- Antihistamines and decongestants: Chlorpheniramine, loratadine (Claritin), pseudoephedrine, zinc-based cold remedies (Zicam)
- Antihypertensives and cardiac medications: Acetazolamide (Diamox), amiloride (Midamor), betaxolol (Betoptic), captopril (Capoten), diltiazem (Cardizem), enalapril (Vasotec), hydrochlorothiazide (Esidrix) and combinations, nifedipine (Procardia), nitroglycerin, propranolol (Inderal), spironolactone (Aldactone)
- Anti-inflammatory agents: Auranofin (Ridaura), colchicine, dexamethasone (Decadron), gold (Myochrysine), hydrocortisone, penicillamine (Cuprimine),
- Antimanic drugs: Lithium
- Antineoplastics: Cisplatin (Platinol), doxorubicin (Adriamycin), methotrexate (Rheumatrex), vincristine (Oncovin)
- Antiparkinsonian agents: Levodopa (Larodopa, with carbidopa (Sinemet)
- Antipsychotics: Clozapine (Clozaril), trifluoperazine (Stelazine)
- Antithyroid agents: Methimazole (Tapazole), propylthiouracil
- Lipid-lowering agents: Fluvastatin (Lescol), lovastatin (Mevacor), pravastatin (Pravachol)
- Muscle relaxants: Baclofen (Lioresal), dantrolene (Dantrium)
Commonly Associated Conditions
URI, allergic rhinitis, dental abscesses