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

Smelling

Loss of smell; Anosmia

The loss of smell can occur due to nasal congestion or a blockage of the nose. It isn't serious, but it can sometimes be a sign of a nervous system (neurological) condition.

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.

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

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.

The sense of smell also enhances your ability to taste. Many people who lose their sense of smell also complain that they lose their sense of taste. Most 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. You may feel rather than smell them.

• Certain medications (such as amphetamines, estrogen, naphazoline, phenothiazines, long-term use of nasal decongestants, reserpine, and possibly zinc-based products)
• Head injury
• Lead poisoning
• Nasal or sinus surgery or disease
• 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 the lost sense of smell. Treatment can include:

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

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

If you lose your sense of smell, you may have changes in taste. Adding highly seasoned foods to your diet can help stimulate the taste sensations that you still have.

Improve your safety at home by using smoke detectors and electric appliances instead of gas ones. You may not be able to smell gas if there is a leak. Or, install equipment that detects gas fumes in the home.

There is no treatment for loss of smell due to aging.

If you have a loss of smell due to a recent upper respiratory infection, be patient. The sense of smell may return to normal without treatment.

Call your health care provider if:

• The loss of smell continues or is getting worse
• You have other unexplained symptoms

The health care provider 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?
• Factors that make it worse
  • 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 health care provider will look at and around your nose. Tests that may be performed include:

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

In some cases, you may need surgery (biopsy) to remove a piece of the cells that help you smell (olfactory epithelium) 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 help keep mucus loose and moving.

Steroid nasal sprays or pills may be recommended.

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

Leopold DA, Holbrook EH. Physiology of olfaction. In: Flint PW, Haughey BH, Lund LJ, et al, eds. Otolaryngology: Head & Neck Surgery. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2010:chap 41.

Baloh RW, Jen J. Smell and taste. In: Goldman L, Ausiello D, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 435.