Impaired smell is the partial or total loss of the sense of smell.

The loss of smell is usually the result of nasal congestion or blockage and isn't serious, but it can sometimes be a sign of a nervous system (neurological) disorder. Loss of the sense of smell may not have an obvious cause.

Some loss of smell occurs normally with aging. In most cases, there is no obvious or immediate cause, and there is no treatment.

Temporary loss of the sense of smell is common with colds and nasal allergies, such as hay fever (allergic rhinitis). It may occur after a viral illness.

The sense of smell is often lost with disorders that prevent air from reaching the part of the nose where smell receptors are located (the cribriform plate, located high in the nose). These disorders may include nasal polyps, nasal septal deformities, and nasal tumors.

Other disorders that may cause a loss of the sense of smell include:

• Alzheimer's dementia
• Disorders of the endocrine system
• Head trauma
• Nervous disorders
• Nutritional disorders
• Tumors of the head or brain

Many medications may change or decrease the ability to detect odors.

Most people who lose the sense of smell can still tell between salty, sweet, sour, and bitter tastes, which are sensed on the tongue. They may not be able to tell between other flavors. Some spices (such as pepper) may affect the nerves of the face and may be felt rather than smelled.

• Drugs (such as amphetamines, estrogen, naphazoline, phenothiazines, prolonged use of nasal decongestants, reserpine)
• Lead poisoning
• Nasal decongestants
• Nasal or sinus surgery
• Natural aging process
• Radiation therapy
• Recent viral upper respiratory infection
• Tracheostomy
• Tumors of the nose or brain

Treating the cause of the problem may correct loss of the sense of smell. Treatment can include:

• Antihistamines (if the condition is related to allergy)
• Changes in medication
• Surgery to correct blockages
• Treatment of other disorders

Avoid using too many nasal decongestants, which can lead to recurring nasal congestion.

If you permanently lose your sense of smell, you can change your diet to include highly seasoned foods and stimulate the taste sensations that you still have.

Be careful to ensure your safety around the home by using smoke detectors and electric appliances rather than gas, or use equipment that detects the presence of gas fumes in the home.

For loss of smell due to aging, there is no treatment.

For loss of smell caused by a recent viral upper respiratory infection, be patient. The symptoms return to normal without treatment. Sometimes zinc supplements are recommended.

Note: Loss of the sense of smell may be temporary, and ability to smell may return on its own, especially after colds or viral infections.

Call your health care provider if the loss of smell continues, is getting worse, or if you have other unexplained symptoms.

The doctor will perform a physical exam and ask questions about your medical history and current symptoms. Questions may include:

• Time pattern
  • When did this problem develop?
  • Have you always had problems with your sense of smell?
  • Is the problem getting worse?
• Quality
  • Are all odors affected or only certain types?
  • Can you taste food?
• Aggravating factors
  • Do you have a cold or other upper respiratory infection?
  • Do you have allergies?
  • Do you have chronic sinusitis?
  • What medications do you take?
• Other
  • What other symptoms do you have?

The doctor will look at your nose and surrounding structures. Tests that may be performed include:

• CT scan
• MRI scan
• Nasal endoscopy
• Olfactory nerve testing
• X-rays of the skull

In some cases, surgery (biopsy) to remove a piece of the cells responsible for smell (olfactory epithelium) may be needed to make a diagnosis.

If the loss of sense of smell is caused by a stuffy nose (nasal congestion), decongestants or antihistamines may be prescribed.

A vaporizer or humidifier may prevent mucus from drying and improve nasal discharge.

Steroid nasal sprays or pills may be recommended.

Vitamin A may be given by mouth or with a shot (injection).