Some Causes and Features of Anosmia
Cause |
Common Features* |
Tests |
Blockage within the nose |
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In people who have chronic allergy symptoms (such as nasal congestion and a clear discharge) No pain Symptoms that often occur during certain seasons or after exposure to specific substances |
A doctor's examination |
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Polyps that are usually seen during the examination |
A doctor's examination |
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Destruction of smell receptors |
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A thick, foul-smelling nasal discharge most or all of the time Previous sinus infections |
A doctor's examination Usually computed tomography (CT) |
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Coronavirus disease 2019 (COVID-19)† |
Loss of smell is often followed by other symptoms of infection (for example, fever or cough) |
Viral testing when available |
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Some viral upper respiratory infections (such as influenza) |
Loss of smell that occurs after an infection |
A doctor's examination |
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Tumors (a rare cause) |
Possibly vision problems or only loss of smell |
CT Magnetic resonance imaging (MRI) |
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Drugs (such as amphetamines, enalapril, estrogen, naphazoline, phenothiazines, and reserpine or use of decongestants for a long time) |
Usually in people who report taking such drugs |
A doctor's examination |
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Toxins (such as cadmium and manganese) |
Usually in people who report exposure to such toxins |
A doctor's examination |
Destruction of olfactory pathways in the brain |
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Progressive confusion and loss of recent memory |
MRI Sequential memory tests |
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In people who have had a head injury |
CT or MRI |
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Degenerative neurologic disorders (such as multiple sclerosis) |
Intermittent episodes of other symptoms of nervous system dysfunction, such as weakness, numbness, or difficulty speaking, seeing, or swallowing |
MRI Sometimes a spinal tap |
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Brain surgery or infection |
In people who have had brain surgery or a brain infection |
CT or MRI |
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Sometimes headache and/or symptoms of nervous system dysfunction |
CT or MRI |
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* Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present. |
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† Destruction of smell receptors has not yet been confirmed as the mechanism for anosmia. |
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