I am way behind in my newspaper and magazine reading, but I came upon an article, “The Forgotten Sense,” which appeared in The New York Times Magazine, by Brooke Jarvis, which was among the most fascinating pieces I’ve read in a long time. The article focuses a lot of attention on the ways in which up to an estimated two-thirds of post-COVID-19 infected patients lose their olfactory senses (and in many instances, their sense of taste, which is intimately connected with the sense of smell). Lacking the sense of smell is hazardous to your health; not being able to detect food poisoning, a burning dinner or a gas leak is, indeed, problematic. “This month,” writes Jarvis, “a Texas family whose members lost their sense of smell to COVID narrowly escaped a house fire after the only uninfected member, a teenager, smelled smoke and woke everyone else up.” Indeed, “Smell is no big deal, until it’s missing.”

Those who have suffered this abnormality struggle “with depression, symptoms similar to those of post-traumatic stress disorder and feelings of relentless isolation and disconnection from the world around them. It felt, some people said, as if they were living their lives in black and white, or trapped behind a sheet of glass; their sense of normalcy and well-being had disappeared with their olfaction. ‘I feel alien from myself,’ one person wrote. ‘Detached from normality. Lonely in my body. It’s so hard to explain.’ Another described feeling ‘discombobulated—like I don’t exist.’”

Our sense of smell is taken for granted and often dismissed as almost irrelevant to who we are as human beings. So many philosophers and scientists—from Plato and Aristotle to Descartes, Kant, and Darwin—have relegated it to the more “primitive” of our five senses, the “province of lesser animals.” But as Jarvis writes:

“Smell is a startling superpower. You can walk through someone’s front door and instantly know that she recently made popcorn. Drive down the street and somehow sense that the neighbors are barbecuing. Intuit, just as a side effect of breathing a bit of air, that this sweater has been worn but that one hasn’t, that it’s going to start raining soon, that the grass was trimmed a few hours back. If you weren’t used to it, it would seem like witchcraft.”

Jarvis notes that there has been a “renaissance” in “smell science” over the last 30 years. Linda Buck and Richard Axel, awarded the Nobel Prize in 2004, identified “the neural receptors that allow us to perceive and make sense of the smells around us. … The revelation opened the door to a new way of understanding the olfactory system, as well as to a new, ever-expanding world of research. A system assumed to be unsophisticated and insignificant turned out to be quite the opposite. Where vision depends on four kinds of receptors—rods and three types of cones—smell uses about 400 receptors, which are together estimated to be able to detect as many as a trillion smells. The complexity of the system is such that we’re still unable to predict how, or even if, a given chemical will be perceived by our olfactory system. The old quest to map odorants and their perception is now understood to be a wildly complicated undertaking. Joel Mainland, a neuroscientist at the Monell Center who is working on the problem, told me that while maps of color vision are easily presented in two dimensions, an eventual olfactory map might require many more.”

Smell is indeed one of the most remarkable senses we have. From its role in detecting hazards to the transmission of pheromones and its role in human attraction to its crucial role in the functioning of our immune system, olfaction is the most underappreciated and least understood of the ways in which the human organism apprehends the world. As Jarvis explains: “While what we see must pass through various parts of the brain before it reaches our centers for memory or emotion, smell has a nearly direct pathway. ‘They’re built together,’ [neurobiologist Sandeep Robert] Datta said of the brain and the chemical world that it perceives. ‘They’re meant to function as a unit.’”

The sense of smell is the only sensory modality in which the actual airborne molecules of the perceived object enter our bodies, attaching to receptor cells that are themselves neurons.  Our olfactory nerves consist of neurons with one end in direct contact with the external world and the other in direct contact with the brain. It may be the most primal, but it is also the most intimate of our sensory modalities, performing an act of neural intercourse every time we take a whiff.

Science is coming to understand the importance of the olfactory sense in more ways than one. Just as some of the recent research has shown an impaired sense of smell in COVID and post-COVID-infected patients, it is often bound up with neural diseases like Alzheimer’s and Parkinson’s, as well as autoimmune disorders, from MS to rheumatoid arthritis to lupus. It is also experienced to a much higher degree by those suffering from depression. Interestingly, it has been found that “children with autism have different automatic sniff reactions than those who are neurotypical, and they use more parts of their brains to process odors. They can also follow social cues better if they can smell a mother’s odor, even if she isn’t present.”

For me, olfaction has never been a “forgotten sense.” It is something of which I am deeply aware. I cannot imagine a world without a sense of smell. It is such a crucial part of my sensory apparatus that I have never taken it for granted.

It also has a way of transporting me to places buried deep in my memory. That acrid smell of burning plastic, metal, and human flesh that inhabited southern Brooklyn in the days after 9/11 is something I will never forget. But it is not just tragic memories that the sense of smell conjures up. Walking through my neighborhood, picking up the scent of fresh baked bread or a pizza emerging from a hot oven can get my salivary glands going immediately. I cannot forget the scent of a brand-new car or of an infant child—a parent, a friend, a partner. Just the scent of a certain perfume or cologne conjures up immense feelings of a particular person, time, and place that are not triggered in the same way as, say, looking at a photo of that same person, time, and place. One whiff of Aqua Velva conjures up whole memories of my Dad, who passed away in 1972 in ways that a photo or a video image cannot. One whiff of Chanel No. 5 conjures up a flood of memories of my Mom, who passed away in 1995, in ways that a photo or a video image cannot.

A greater understanding of the “forgotten sense” is one of the more welcome scientific by-products to have come out of a tragic pandemic. Let us hope that research continues to unlock not only the mysteries of COVID, but the continuing mysteries of how our organisms function—and why it is so important to recognize when something so crucial to being human is just not functioning the way it should.