Why are Humans Losing Their Sense of Smell?

What are the Consequences?

In an earlier article “The Tragic Trend in Infants' Hearing Loss: As We Alter Nature, It Alters us in Return!,” I explained how hearing losses are becoming common in larger cities and industrial areas, particularly among babies and newborns. I reported and analyzed a 500% increase in neonatal hearing loss. In today’s article, I would like to discuss the loss of another sense in modern (denatured) humans: Smelling!

The Most Important Sense?

Evolutionarily, the olfactory system is so crucial for our survival and adaptation upon detecting odor cues that unlike all other senses, odor information is sent directly from the nasal cavity¹ to the olfactory cortex in the brain without being relayed by the thalamus, the brain’s sensory relay and integration center. In fact, the part of the human brain responsible for emotions, memory, sensations, sensory relays and hormonal moderation, which is called the “limbic brain,” has been called the “rhinencephalon” in the past, derived from the Greek words rhis, meaning "nose", and enkephalos, meaning "brain. The “Nose Brain” of humans and other mammals, controls our brain’s most important basic functions of detecting danger and rewards through our senses, and memorizing them in association with our senses, particularly the olfactory.

Many mammals, including dogs, bears and mice, largely depend on olfaction for sensing the external world—more than humans do—and that their behaviors heavily depends on olfaction.

In humans, because smell is directly processed in the primary olfactory cortex in the brain, odors bypass the conscious “contextual memory” registration in the brain (in the hippocampus) so they can bring back memories without us understanding why.

Our First Line Of Defense Against Airborne Pathogens

It is known that environmental factors such as air pollutants, pesticides and chemicals, fine particulate matter such as those released from automotive tires while driving, and respiratory viral infections (like COVID-19 infections) can cause nasal inflammation and impairments. This is part of our body’s immune system to block the entry of unwelcome harmful agents (pathogens) into our lungs and the brain.

To protect us against harmful microorganisms and allergens, the nasal cavity is supplied continuously with mucous secretion containing immunoglobulin A (IgA). These IgA antibodies are an important part of our immune system and mediate protection mainly by inhibiting microbial attachment and the absorption of molecular antigens, including potential allergens. In response to threats, for example by fine particulate matters, our immune system also releases pro-inflammatory molecules (cytokines) in the nose.

Regardless of whether it results from an external trigger (e.g., environmental allergens, irritants, air pollutants, or microbes) or an underlying intrinsic immune dysregulation, sinonasal inflammation causes symptoms of nasal congestion, drainage, and, in many cases, a diminished sense of smell.

Like all other immune system mechanisms, runny and stuffy nose and a diminished sense of smell are all beneficial when activated “temporarily” in response to short-term stressors. When chronically activated, olfactory defense mechanisms can be troublesome. For example, olfactory impairments have been associated with neurobehavioral diseases and mental illnesses such as schizophrenia, depression, Alzheimer’s and Parkinson’s diseases. In fact, researchers now believe olfactory inflammatory processes are involved in the pathophysiology of schizophrenia and depression. In other words, if infections and pollutions lead to psychological and mental diseases, it’s the dysfunction in smelling and tasting senses that is the precursor and pathway to these diseases. Remember, evolutionarily, humans remember and associate rewards with their aroma and flavor so it is reasonable to expect what I call “dissociative disorders” in my book, such as depression and schizophrenia, after losing our sense of smell or taste.

In fact, we know that brain-damaged animals like salamanders, frogs and fish can replace and regenerate large parts of their destroyed brains only if sensory olfactory nerves are intact and can grow back into the damage area to stimulate ependymal cells in the brain ventricles to proliferate and differentiate into glial cells and neurons. This shows the importance of healthy olfactory neurons in sending vitality signals to the brain’s regenerative algorithms in times of stress and damage.

Modern Denatured Life

The problem with modern life is that in addition to chronic inflammation of our nasal passages (such as olfactory epithelium), we are all also naturally losing our sense of smell over time because our rewards and threats are mostly not associated with natural odors and flavors. Research has shown that “odor deprivation” leads to shrinkage in the part of brain responsible for receiving olfactory signals (called external plexiform layer, EPL). In other words, like all other senses, if we don’t use it we WILL lose it!

So the brains of modern humans are odor-deprived both because of chronic inflammations and lack of sensory input caused by humans spending most of their life indoors and around denatured food with artificial additives, flavors and aromas.

Our body and brain cannot associate these synthetic (artificial man-made) aromas and smells with any natural phenomena, rewards or threats as experienced by our ancestors. The artificial flavor added to a candy or cereal that tastes and smells like banana, may be sensed by the brain as a banana-like substance but our brain is too smart to be fooled because the chemical used as artificial banana flavor “isoamyl acetate” is only one of the “hundreds” of compounds that in a naturally-ripened banana produce its flavor and aroma². Furthermore, isoamyl acetate, like many other man-made chemicals, is detected by our body as harmful and even listed as a hazardous substance. In fact, breathing Isoamyl Acetate can irritate the nose, throat and lungs. Exposure to high concentrations of Isoamyl Acetate can cause headache, drowsiness, dizziness, lightheadedness, fatigue, and may cause you to pass out! All of these signals are indicators that this is not a welcome molecule in our nose and brain. The synthetic flavor is considered “dangerous” to life at exposure levels of more than 1%³.

So the next time you use artificially colored or flavored food (cereals, candy, cookies, chewing gums, cake mixes, etc.), artificial deodorants, soaps and shampoos, remember that your brain may be smelling or tasting an aroma but it is fighting against it at the same time with nasal inflammations or headaches. Unfortunately, many public spaces now embed artificial air fresheners in their ductwork and air circulating systems so it is becoming impossible to escape “fake” aroma that may trigger our immune system and cause chronic olfactory inflammations.

Constant exposure to odors and molecules that cause olfactory or respiratory inflammations is associated with psychological and mental diseases, as explained earlier. Studies now show that exposure to air pollutants and harmful odors during childhood is associated with impairment of attention, memory, and learning abilities, asthma and increased risk for schizophrenia.

Many children today suffer from olfactory discrimination disorder and are unable to recognize familiar or very common smells. So they can accidentally eat spoiled food or nonedible, potentially harmful substances and are unable to detect hazardous chemical or burning odors. Many other children suffer from olfactory avoidance which means they often have extreme or upsetting reactions to even very mild stimulation. These are all telltale signs that we are exposing our children to artificial settings and foods with harmful olfactory stimuli and depriving them of natural settings and foods.

Some 40 million Americans were believed to suffer from Anosmia (which means loss of the sense of smell⁴) and hyposmia (which means reduced smell sensitivity) even before COVID-19. It has been established that our sense of smell can be impaired by many chemicals and pharmaceuticals (including heavy metals, inorganic and organic compounds, acids and pollutants, stimulants such as amphetamines and cocaine, depressants such as morphine, antibiotics and other drugs, including the vasoconstrictors in nasal sprays), as well as metabolic and hormonal imbalance (as in insulin resistance, diabetes, Cushing's syndrome and hypothyroidism).

As explained in my upcoming book “The Rogue Brain” (available on Amazon soon), retraining our brains and senses with natural stimuli is the first step in gaining control of our metabolic health.

1. Perceived by olfactory sensory neurons (OSNs) in the olfactory epithelium (OE) inside the nasal cavity and transmitted to the brain’s cortex via the olfactory bulb (OB).

2. https://www.inverse.com/science/artificial-banana-flavor-real-science

3. https://pubchem.ncbi.nlm.nih.gov/compound/31276#section=Immediately-Dangerous-to-Life-or-Health-%28IDLH%29

4. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/anosmia-loss-of-smell