You Smell Like Death

Most people use their sense of smell to navigate the world.

Smells enrich the world arounds us, help form memories, warn us about danger or elicit pleasure responses. A few poor individuals have lost all ability to use their nose to sense their surroundings; and, of course, there is a fancy word to describe such a condition — Anosmia. Anosmia can be caused by a multitude of things– from a well placed fist shattering the nasal bone to nasty microbes causing serious sinus infections – one can easily loose the ability to smell. There is even a hypothesis that, for a very small percentage of individuals, an impaired ability to smell may be an early indicator of neurodegenerative diseases. Now, don’t panic because your ability to pick up on the warm scent of baked bread or bacon sizzling away in a pan has diminished – there is probably a much less insidious reason for your lack of olfactory precision.

A Nose By Any Other Name Will Smell As Sweet

neuroscience_exploring the brain
Image: Neuroscience: Exploring the Brain. 2007.

Your ability to smell is a pretty neat little trick and is, in fact, a fairly complicated neurophysiological process. Some wormy looking neurons hang out in a bony plate at the top of your nasal cavity. They possess projections called cilia (these guys are found in an astounding number of cells) and these cilia have a little receptor on the tip that odour molecules like to attach themselves too.

A nice cellular hug.

It snaps, crackles and pops some information up the neuronal cell, buzzes through the boney plate and sends the signal along to specific regions – all on a magic carpet of sorts called an olfactory bulb. This bulb sends on this information to higher brain centers to be interpreted.

Receptors that have similar molecular make up all cluster together in zones on the olfactory blub– this clustering forms a spatial map of highly ordered information.

It’s pretty crazy how these tiny cells organize smells into bits of electricity that form organized information like the colour pegs of a light bright. (Are those still a thing? Does anyone born after 1989 have any idea what I am talking about? A quick google search has informed me you can buy one (here) on for the low price of 70 dollars. Yikes, the price of nostalgia is high.)

So, now that you have been primed from this butchered crash course style explanation of the olfactory system – lets continue on this fantastic journey.

Touchy Tingley Feelings and Things

I would imagine a lot of people are familiar with the fact that smells induce some pretty strong emotional responses from us humans. It has a lot to do with the fact that a little brain structure called the amygdala has its gummy little fingers digging around in our odor evoked memories. The amygdala, adorably named for it’s little almond shape, is located snuggly in your medial temporal lobe and is notorious for emotional perception and processing.  There appears to be a direct line of communication from the olfactory blub and its tracts (fancy word for “nerve fibers”) to the limbic system, where the amygdala hangs out. The amygdala receives a lot of information from our noses and tends to put emotional significance to them.

Smells like our favourite food or the smell of our lover can elicit emotional and, generally, pleasurable, responses. Smells like sulfur, methane or the unmistakable smell of something burning warn us of danger. We are conscious of how theses things smell (you probably thought about it as soon as you read the words) and we have a learned response that makes it possible for us to interpret and react to the stimuli.

This all makes sense to us. We can describe them. We can personally confirm that we experience it.

We perceive it, therefore it’s our reality. And it appears to be a pretty universal experience among other humans, which helps us solidify that reality.

But there is a deeper journey for us in the sinus cavity.

What’s that Smell?

As I mentioned earlier – the loss of smell is thought to be a possible warning sign for neurodegenerative diseases like Parkinson’s disease (PD). But, does PD have a smell?

That is to say, does neurodegeneration, or any disease state, have its own odour?

Well, apparently Parkinson’s has an oily musky scent to it.

Eye brow raising, no?  How, the hell?

The question is then: Is that even possible?

As in any good story, let’s suspend our disbelief for a moment and take a look at the tale of the woman who can smell Parkinson’s disease.

Joy and her Husband, Les.  Credit:  Dailymail

Joy, a nurse from England noticed her husband’s scent changed. Over the course of a few years, his familiar smell began to slowly morph into an unsettling foreign odor. She scolded her husband, a physician, that he was falling behind on his hygiene. He became annoyed and assured her nothing in his routine had changed. She describes the change in his smell as a gradual one, over the course of a few years it would creep up again and again. Six years after the onset of this shifting scent profile, her husband was diagnosed with Parkinson’s disease. Upon returning from a Parkinson’s support group, she told her husband about a startling realization she had – all of the individuals from the meeting had the same smell.

Joy eventually shared her smell-related hypothesis to a researcher at a Parkinson’s meeting in Scotland. Scientist, Dr. Tilo Kunath, is head of a research initiative in neurodegenerative medicine at the University of Edinburgh. (Interestingly, he has a Canadian connection — obtaining his PhD from the University of Toronto, investigating novel stem cell systems.)

Dr. Kunath took some interest in the idea and decided to test Joy’s alleged ability to sniff out Parkinson’s. Given T-shirts from 6 controls and 6 PD suffers she was tasked to accurately identify which clothing belonged to which group, based only on the information her olfactory system gave her. In the end Joy identified all correctly, save for one subject. She insisted a control participant belonged in the Parkinson’s group.

Are you waiting for the plot twist here? I know you can smell it coming.

Less than a year later, the “incorrectly” identify control participant was diagnosed with Parkinson’s disease.

Currently, Dr. Kunath and his team are using her nose to identify the unique molecules that make up Parkinson’s signature scent. This identification could lead to a diagnostic test that can use fancy science instruments, like mass spectrometry (mass spec to his friends) to interpret a patient’s scent profile. A way to come back with a diagnosis sooner in hopes to better manage the disease progression.

Now, according to the comments on the news stories I have read while researching for this post, Joy is not alone in her abilities. My personal favourite description is one man’s confirmation of the musky signature, adding that it is much more gamey – like when one cooks moose or bear meat.


Now, using our senses to identify disease is not an unfamiliar concept. For example, as a nursing student, I was taught that breath that has a fruity odor is indicative of Diabetic Ketoacidosis, a life-threatening condition when insulin levels are insufficient and blood sugar levels become dangerously high. It’s the smell of ketone bodies escaping the body – a sign that your cells aren’t taking in the glucose they need so they resort to burning other your muscles or fat.

Using good old Diabetes as an example again, the name itself, Diabetes Mellitus, comes from the senses once again being utilized as a diagnostic tool. Mellitus means “honey sweet” and came into being after a nice sip of a patient’s urine. The urine carried a sweet taste (from excess glucose spilling into it) and was a way to recognize the condition.

Pour me a pint of that Honey Sweet.

For some reason, one woman’s ability to pick up on a scent that no one else can is going to breed a healthy sense of skepticism. And holy shit it should. The day it doesn’t is a sad day for humanity and I don’t want to be alive to see it.

Until her mapping of scent profiles can be categorized, accurately tested, accurately identified by the mass spectrometry or any other diagnostic tool and, more importantly, be consistently reproducible, the story should leave you feeling a little skeptical.

It’s a great story, but is there any science caught in its nose hairs?

Send in the Hounds

Dogs are notorious for their ability to sniff out all kinds of things and we have been using them for centuries. From finding foxes cowering in their dens to bombs, drugs and thugs — we have harnessed the power of the canine nose.

Recently that went next level. Dogs have now been used as furry blood sugar monitors, warning their owners when their blood sugars start to rollercoaster. A feat that seems a little supernatural in itself.

Recently, there have been studies conducted to see if dogs can be used as diagnostic tools in cancer identification. This was tested through the sniffing of breath, urine and other bodily fluids.

Overall, the dogs performed pretty well. When tested to see if they can discriminate lung cancer from COPD (chronic obstructive pulmonary disorder) in breath samples the dogs had a sensitivity rate of 71% and a specificity rate of 93% — the dogs were able to pick up the scent more times than chance would account for and were then able to discriminate between different smell profiles 9 times out of 10.

Another study used urine as the vehicle for cancer’s smell. This time it was a test to identify the presence of prostate cancer. The dogs in this study had a very high sensitivity rate (98.6%) and specificity rate of 96.4%. A promising find, as PSA (prostate specific antigen) serum (blood) testing  doesn’t have a great track record for its ability to accurately assess a man’s prostate cancer risk. A high serum PSA does not equate a malignant condition and often men go through painful, risky prostate biopsies to rule out cancer. The outcome of said biopsies may be a benign result and some less than desired complications that lead to loss of function. Sorry guys.

Now, the future is not a German Shephard in a lab coat hanging out in an medical laboratory waiting patiently for urine and breath samples to analyze.

But the future of scent diagnostics might be in the development of electronic noses.

E- noses may, eventually, become a diagnostic tool to accurately identify various types of cancers. There are dozens of studies testing the efficacy of a robot nose to detect cancer at the earliest stage possible in order to maximize survival rates. However, these E-noses have been tested for several years and are still in their infancy. It will be a long while before the Electro nose is hanging out in your standard diagnostic lab.

Volatility and Psychic Cats that Sense Death

So what does a nurse from England, a German Shepard and a electronic nose have in common?

They all may able to pick up on something called volatile organic compounds or VOCs.  We all apparently have an odour fingerprint and according to one study (THIS ONE) infections and certain disorders can produce new VOCs or change which molecules in our repertoire are the most pungent – essentially changing how we smell.

Something that is not likely to be picked up consciously, if at all, by the rudimentary human olfactory system.  Dogs and machines, perhaps.

What about cats?

Oscar. Image:

For centuries, these adorable furry felines have been associated with death. The Ancient Egyptians worshiped them and regarded them as guardians of the underworld.

When Christianity came around, cats were thought to be consorts of Satan; demons in fur suits that whisper in the ears of witches.

I have a point I am getting to I swear.

There is another great story, this time it’s about the cat that can “accurately” predict when someone is about to die. His name is Oscar and he lives in a nursing facility. When Oscar pays you a visit and curls up at your feet, chances are you are not going to live to see another day. You can read about Oscar (HERE).

So, is Oscar using VOCs to accurately foretell the deaths of the poor souls he visits or is he a consort of Satan?

All questions of the natural world have answers; sometimes we just don’t have access to them yet.

My money is on the smells. Sorry Satan.

Skeptical Sighing

From nurses who smell Parkinson’s to Cats who can sense death, there are a couple things to package up and take home with you

Let’s finish off where we began — your olfactory system. This little guy is so wonderfully complex and beautifully orchestrated. It helps you interpret your world, form memories and evoke emotions. From the aromas that help you get the most out of your wine or whiskey to the putrid smell of a natural gas leak – your nose and its neurons are there for you

Next, never underestimate the power of a good story. They can be seductive. They can overwhelm our senses and our reason. Beware the beguiling narratives.

Third, stay skeptical in everything you do. Never stop questioning. That’s the only way you are going to get any answers. I hope you asked yourself, how the hell can someone smell the decay of the nervous system? Because, yeah that’s weird. How can we test it and how can we disprove it? Also a good question.

We will see if Joy can accurately identify PD’s scent profile. Then we will let biochemists and finely tuned equipment see if they can accurately detect it in those afflicted. Until then, we can enjoy the story but err on the side of caution.

Lastly, the next time you see a dog, imagine them in whimsical lab coat. You’re welcome.


Neuroscience: Exploring the Brain
Olfactory System of Highly Trained Dogs Detects Prostate Cancer in Urine Samples. 2014
Canine scent detection in the diagnosis of lung cancer: revisiting a puzzling phenomenon. 2011
Sniffing out cancer using JPL electronic nose: A pilot study of a novel approach to detection and differentiation of brain cancer. 2009
The scent of disease: Volatile organic compounds of the human body related to disease and disorder. 2011
Woman who can smell Parkinson’s disease helps scientists develop early detection test. CBC. 2017
A Day in the Life of Oscar the Cat. 2007




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