The common cold with nasal congestion is the most common cause for a partial, temporary loss of smell. Obstruction in the nasal passages, particularly from polyps or nasal fractures, also is common. Normal aging also may cause a loss of smell, which may be progressive, becoming complete and permanent.

What is smell?

Smell results when individual molecules, suspended in the air, are inhaled and attach to receptors in the mucous membranes of the nose, stimulating nerves that connect directly to the brain. Any problem within this olfactory system — congestion or obstruction in the nose, inflammation of its lining, nerve damage, or altered brain function — affects your ability to smell normally.

While total loss of smell is fairly rare, and the more common causes improve with time, symptoms are sometimes severe enough to result in significant problems or distress. An intact sense of smell is necessary to accurately taste and enjoy food; losing this sense could cause you to lose interest in eating, potentially leading to weight loss, malnutrition or even depression.

Problems with the inner lining of your nose

Conditions that cause temporary irritation or congestion of the mucous membranes lining the inside of your nose are the most common cause of loss of smell. These may include:

  1. Acute sinusitis (sinus infection)
  2. Common cold
  3. Hay fever (allergic rhinitis)
  4. Influenza (flu)
  5. Nonallergic rhinitis (chronic congestion or sneezing not related to allergies)

Obstructions of your nasal passages

Conditions or obstructions that block the flow of air through your nose can include:

  1. Bony deformity inside your nose
  2. Nasal polyps
  3. Tumors

Damage to your brain or nerves

Less commonly, the nerves leading to the olfactory center of the brain or to the brain itself can be damaged or deteriorate due to:

  1. Aging
  2. Alzheimer's disease
  3. Brain aneurysm
  4. Brain surgery
  5. Brain tumor (both cancerous and noncancerous)
  6. Chemical exposures to certain insecticides or solvents
  7. Diabetes
  8. Huntington's disease
  9. Kallmann's syndrome (inability of testicles to produce sperm)
  10. Klinefelter syndrome (a condition in which males have an extra X chromosome in most of their cells)
  11. Korsakoff's psychosis (a brain disorder caused by the lack of thiamin)
  12. Malnutrition
  13. Medications (for example, some high blood pressure medications)
  14. Multiple sclerosis
  15. Multiple system atrophy (MSA) (a progressive disorder of the nervous system)
  16. Paget's disease of bone (a disease that affects your bones, sometimes facial ones)
  17. Parkinson's disease
  18. Pick's disease (a form of dementia)
  19. Radiation therapy
  20. Rhinoplasty
  21. Schizophrenia
  22. Sjogren's syndrome (an inflammatory disease that generally causes dry mouth and eyes)
  23. Traumatic brain injury
  24. Zinc deficiency
  25. Zinc-containing nasal sprays (taken off the market in 2009)

Causes shown here are commonly associated with this symptom. Work with your doctor or other health care professional for an accurate diagnosis.

Nov. 16, 2016