Fifteen Facts about the Olfactory Nerve — The Sense of ‘Smell’

Joseph R. Anticaglia MD
Medical Advisory Board

The sense of smell is often downplayed compared to the other special senses such as vision or hearing. But the Olfactory nerve, smell nerve, is an important factor in the quality of our life. It gives us pleasure, plays a role in nutrition and is our early warning system against danger, such as rancid food or a gas leak. Below are facts about the Olfactory nerve.

Ten Facts:

  1. Olfactory nerve, the smell nerve, is located in the upper-back part of the nose. It’s about the size of a postage stamp, one square inch.
  2. The sense of smell is a key player in our ability to taste. Eighty percent or more of what we refer to as taste is related to smell
  3. Flavor is fundamentally a fusion of smell and taste.
  4. Taste is different from flavor. Taste refers to the five primary tastes — sweet, bitter, sour, salty and umami.
  5. Anosmia is the complete loss of the sense of smell. It can be temporary or permanent. It’s underappreciated and under tested.
  6. Anosmia can be an early sign of Alzheimer’s or Parkinson Disease.
  7. After the age of 65, one study suggests that a significant deficit in the sense of smell (anosmia) is associated with increased mortality.
  8. Smell cells can grow back. Sometimes they don’t.
  9. Retronasal Olfaction means we can smell through the back of the mouth in addition to sniffing odorants through the nose. When chocolate melts and enters the back of the mouth, the aroma goes upwards towards the nose and the receptor cells of the Olfactory nerve. It’s the aroma of chocolate, the sense of smell that distinguishes it from the flavor of butterscotch.
  10. We smell the fragrance of flowers, the aromas of food with our brain. Chemicals in the air are sniffed through the nose or back of the mouth and relayed to the brain for interpretation.

Plus Five:

  1. Some lose the sense of smell without a good explanation and it returns to normal just as mysteriously. The cause of anosmia is unknown in about 25% 0f the time…
  2. Radiation therapy, surgery, medications and trauma can damage your sense of smell.
  3. Women, in general, identify fragrances, aromas and odors more accurately than men.
  4. Lack of smell can prevent us from detecting spoiled foods, gas leaks or smoke from fires.
  5. Treatment depends on what caused the loss of smell. Was it due to nasal polyps, a facial fracture or a tumor? Is the loss due to a vitamin or mineral deficiency? Unknown cause?

According to the NIH, one to two percent of Americans report difficulties with the loss of smell. Tumors, genetics and other conditions affect the sense of smell. Many feel frustrated and become more isolated. People afflicted with such a loss are robed of the pleasures in life, in particular, the enjoyment of food and drink and its social aspects.


  1. Davangere, P. et al; Olfactory Identification Deficits and Increase Mortality in Community; Journal of Neurology, July 3 2015
  2. Costanzo RM; Regeneration of Olfactory Receptor Cells; Pub Med; Ciba Foundation Symposium, 1991
  3. Anticaglia, Joseph R; Taste & Smell — The Olfactory Nerve -The Five Senses; HC Smart, 2016
  4. Bromley, Steven M.; Smell and Taste Disorders; Am. Fam. Physician; Jan 15, 2000.
  5. NIH; Smell Disorders; August 5, 2015.
  6. Anticaglia, Joseph R; Taste & Smell — The Five Tastes; HC Smart, 2016

This article is intended solely as a learning experience. Please consult your physician for diagnostic and treatment options.