Douglas Lobay, BSc, ND

Old Spice cologne smells like a blend of anise, cinnamon, cloves, nutmeg, orange, pimento, and black pepper.  It has a distinctive odor that is popular among middle-aged men.  My father used to use Old Spice aftershave and cologne. I liked my father.  I still remember the sharp fragrance as something strong, masculine, and wild. It used to permeate the bathroom and filter through our house. Nowadays I use Old Spice. 

The school that I attended as a child and teenager was only three blocks from my family home.  I used to walk to school every morning and walk back every afternoon.  There was a short cut to our house that involved walking on a path through an empty field next to our house.  The field was overgrown with different grasses like ryegrass, fescue and timothy, alfalfa, clover, and wild mustard.  Crickets and grasshoppers played a mellifluous symphonic harmony in the field every evening.  On many warm sunny days when the sun was golden, I can remember walking home from school in the afternoon to the sweet aroma of fresh bread that my mother was baking.  The aroma permeated the air, and by the time I got home I was salivating in anticipation of eating a slice of fresh bread.

In my naturopathic practice I have been recently pondering the clinical utility of pleasant fragrances.  From an evolutionary perspective, odors and smells can have an adaptive function.  Pleasing odors can evoke a sense of calm and happiness.  They can indicate that something is safe and nurturing. Bad odors alternatively can be a forewarning of impending harm and danger.  They can evoke strong responses to evade and avoid something.  This adaptive behavior is an integral part of the survival mechanism of an individual and the species.

Bad odors that elicit a negative response in the nervous system include adjectives like acrid, fetid, foul, malodorous, putrid, smelly, and stinky. Examples of substances that elicit these negative responses include bad breath, decaying material, excrement, flatulence, garbage, harsh chemical odors, rotten food, smoking, sewage, and human sweat. Exposure to these odors elicits a negative response and usually causes the organism to avoid the substance.  As a byproduct of evolutionary adaptation, or grand design, this makes sense because these substances are often bad and harmful to the organism. 

Good odors that elicit a positive response in the nervous system include adjectives like sweet, fragrant, aromatic, pleasant, pleasing, and pungent. Examples of substances that elicit a positive response include coconut, fresh-brewed coffee, a burning fireplace, fresh roses and other fragrant flowers, fresh air, spices like cinnamon, peppermint and vanilla, fresh-baked cookies, morning dew, perfume, pizza, and sea water. Exposure to these odors elicits a positive response and usually causes the organism to gravitate towards the substance.  As a byproduct of evolutionary adaptation or grand design, this makes sense because these substances are often good and beneficial to the organism.

Physiologically the detection of odors and smells is known as olfaction.  Olfaction is one of the basic five human senses and serves an important role in protecting the organism and promoting its survival. The olfactory region is located in the upper nasal cavity near the cribiform plate bone that separates the nasal passages from the brain.  The olfactory area consists of about fifty million specialized nerve cells in the nasal mucosal lining.  These neurons are concentrated in two discrete areas that measures 1.6 square inches or 10 square centimeters in total dimension.  The nerve cells transcend the cribiform plate and coalesce in a collection of nerve cell bodies called the olfactory bulb. 

The ratio of convergence in primary olfactory neurons is about 1000:1; that is, approximately one thousand olfactory sensory neurons converge to form a glomeruli or conglomeration of neuron cell appendages. From there some of the neurons go directly to the olfactory center of the cerebrum located in the posterior inferior temporal cortex. Other neurons converge to form a collection of presynaptic axons with postsynaptic dendrites called olfactory glomeruli. The postsynaptic neurons are known as mitral cells and distribute information to five different areas of the brain for processing, including the amygdala. Because of this connection to amygdala and other parts of the limbic system, odors can elicit a strong emotional response and is tied into long-term memory.¹

Some interesting facts about human smell include that every individual has a unique odor. Women generally have a better sense of smell than men. Humans were originally thought to be able to smell only about 10,000 different odors, but more recent research indicates that the number is close to a trillion. Humans were originally thought to have five and six million olfactory neurons, but now that number is around fifty million. 

Dogs have 44 times more or 220 million olfactory neurons and have a sense of smell that is 100 times stronger than a human.  A grizzly bear is believed to have the best sense of smell of any land mammal and is 2,100 times stronger than a human. It can detect an odor from up to twenty miles away from its source. 

The olfactory nerve system is the only cranial nerve that can regenerate itself.  Olfactory nerves can regenerate every thirty to sixty days.

Humans can smell negative emotions like anger, fear, and disgust. Humans can also smell positive emotions like love, peace, and happiness. An abnormal disruption of smell is strongly associated with diseases that cause neurological degeneration like Alzheimer’s disease and Parkinson’s disease.¹

A review of organic chemistry reveals the structure of aromatic compounds that are naturally found in food and plants. Aromatic chemicals tend to be carbon based, small to medium in weight, and can easily dissolve in the water-based mucous membrane lining the olfactory region. These compounds include a broad classification of esters, terpenes, cyclic aromatics, amines, alcohols, aldehydes, ketones, lactones, and thiols. The fragrant chemicals must dissolve in air, travel through the nasal passages, and be soluble in the mucous membrane before reaching binding sites on sensory olfactory neurons.  The binding site is believed to work like a lock and key mechanism—that is, only specific chemicals can bind to specific binding sites to evoke an action potential of that neuron.¹

The effect of lavender aroma on anxiety was studied in 80 patients undergoing bone marrow biopsy. Smelling lavender for 15 minutes prior to having this procedure done significantly lowered anxiety levels.²

The efficacy of lavender oil was evaluated for anxiety and pain in 106 patients undergoing peripheral venous cannulation. There was a statistically significant decrease in levels of anxiety and pain and a higher level of satisfaction in those individuals who smelled lavender oil prior to peripheral venous cannulation.³

The effect of lavender and chamomile essential oil on anxiety levels was studied in 120 hospital-based nurses. A symptom-based analysis revealed that anxiety levels were statistically lower in those nurses who were exposed to lavender and chamomile, with or without concomitant music therapy, prior to the work shift at the hospital.⁴

The correlation between smell and levels of anxiety and depression were studied in 337 individuals, many of whom suffered with irritable bowel syndrome. A significant positive correlation was observed in patient’s levels of anxiety and depression and smell disturbance.  The greater the smell disturbance, the greater the potential for anxiety and depression.⁵

A systematic review of eleven randomized controlled and quasi-randomized controlled trials were evaluated.  Compared to controls, the most common use of aromatherapy that included lavender and orange fragrances was effective in reducing levels of anxiety prior to dental procedure. Aromatherapy was more effective than music therapy and reduced levels of pain, anxiety, and moods better than placebo.⁶

From a naturopathic perspective I believe the clinical utility of fragrances is primarily involved in the treatment of anxiety, depression, and their allied comorbidities in physical ailments.  The exact fragrance may be specific to the patient based upon their past experience, distant memory, and current preference. Once identified as a positive, pleasant, and pleasing fragrance, the odor can be then used to treat a condition. Like positive reinforcement a fragrant odor can induce a pleasant flashback and thereby stimulate neural pathways.  If the odor is associated with love, joy, and happiness, then it can stimulate the same emotional feeling. In this way a known, pleasant odor can elicit a positive response.^7-9

It should also be mentioned that other nutritional factors are important in the sense of smell.  In particular, zinc, vitamin A, vitamin B12, vitamin C, and vitamin D are utilized in smell.  Zinc is an important nutrient involved in maintaining tissue barriers such as the nasal epithelium, preventing viral entry into cells, enhancing immune response, and maintaining redox potential. It is also important to note that taking high doses of zinc over prolonged periods can cause anosmia and decreased sense of smell. Air pollution, smoking, and poor diet and nutrition can directly contribute to a decreased sense of smell over time.  Prolonged use of intranasal steroids have been associated with anosmia and decreased smell. The use of illicit intranasal drugs like cocaine can also damage olfactory membrane and neurons. Also, viral infection like Covid-19 can directly damage olfactory neurons in the nasal passage and cause poor smell.

Every spring I would walk downtown to Syd’s confectionary store on Market Street in our small town.  The store was loaded with candy bars, pixy sticks, licorice pipes, pop rocks, and ice cream. The store had the biggest selection of comic books and magazines that I had ever seen. And it even had a pool table and cigarettes.  As I was walking on one particular street, I would stroll by a grove of lilacs.  The lilac florets of deep purple and eggshell-white gave off a fragrant floral aroma of lavender and vanilla.  The smell was intoxicating and sweet.  I would often close my eyes and imbue the fragrant aromas as I walked to Syd’s store. I love the smell of lilacs.  It makes me happy.

References

1. Sarafoleanu C et al. The importance of the olfactory sense in the human behavior and evolution. J Med Life. 2009 Apr 15:2(2):196-198.
2. Abbaszadeh R et al. The Effect of Lavender Aroma on Anxiety of Patients Having Bone Marrow Biopsy. Asian Pac J Cancer Prev . 2020 Mar 1;21(3):771-775.    
3. Karaman T et al. Evaluating the efficacy of lavender aromatherapy on peripheral venous cannulation pain and anxiety: A prospective, randomized study. Complement Ther Clin Pract. 2016 May;23:64-8.
4. Zamanifar S et al. The Effect of Music Therapy and Aromatherapy with Chamomile-Lavender Essential Oil on the Anxiety of Clinical Nurses: A Randomized and Double-Blind Clinical Trial. J Med Life. 2020 Jan-Mar;13(1):87-93.
5. Liu J et al. Subjective Taste and Smell Changes in Conjunction with Anxiety and Depression Are Associated with Symptoms in Patients with Functional Constipation and Irritable Bowel Syndrome. Gastroenterol Res Pract. 2021 Sep 18;2021:5491188.
6. Cai He et al. Efficacy of aromatherapy on dental anxiety: A systematic review of randomised and quasi-randomised controlled trials. Oral Dis. 2021 May;27(4):829-847.
7. Stierwalt S.Why Do Smells Trigger Memories. Scientific American. June 29, 2020. https://www.scientificamerican.com/article/why-do-smells-trigger-memories
8. Fields H. Fragrant Flashbacks. Association for Psychological Science. March 28, 2012. https://www.psychologicalscience.org/observer/fragrant-flashbacks.
9. Kappler M. Like the smell of vanilla? So does the rest of the world. April 8, 2022. Healthy Living. https://www.healthing.ca/wellness/sense-of-smell-cultural-vanilla?

Published Jun 3, 2023

About the Author 

Douglas G. Lobay is a practicing naturopathic physician in Kelowna, British Columbia. Dr. Lobay graduated with a Bachelor of Science degree from the University of British Columbia in 1987. He then attended Bastyr College of Health Sciences in Seattle, Washington, and graduated with a Doctor of Naturopathic Medicine in 1991. While attending Bastyr College, he began to research the scientific basis of natural medicine. He was surprised to find that many of the current medical journals abounded with scientific information on the use of diet, nutrition, vitamins, and botanical medicines. Besides practicing naturopathic medicine Dr. Lobay enjoys research, writing and teaching others about the virtues of good health and nutrition. He has authored several books, numerous articles, and papers and has taught many courses at seminars and colleges throughout his career. He is married to Natalie and has two daughters, Rachel and Jessica. He also enjoys hiking, hockey, skiing, tennis, travelling and playing his guitar.