Merck Manual

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Some Causes and Features of Anosmia

Some Causes and Features of Anosmia


Common Features*


Blockage within the nose

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

Polyps that are usually seen during the examination

A doctor's examination

Destruction of smell receptors

A thick, foul-smelling nasal discharge most or all of the time

Previous sinus infections

A doctor's examination

Usually computed tomography (CT)

Loss of smell is often followed by other symptoms of infection (for example, fever or cough)

Viral testing when available

Loss of smell that occurs after an infection

A doctor's examination

Tumors (a rare cause)

Possibly vision problems or only loss of smell


Magnetic resonance imaging (MRI)

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

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

Progressive confusion and loss of recent memory


Sequential memory tests

In people who have had a head injury


Intermittent episodes of other symptoms of nervous system dysfunction, such as weakness, numbness, or difficulty speaking, seeing, or swallowing


Sometimes a spinal tap

In people who have had brain surgery or a brain infection


Sometimes headache and/or symptoms of nervous system dysfunction


* Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present.

† Destruction of smell receptors has not yet been confirmed as the mechanism for anosmia.