If Your Nose Runs, And Your Feet Smell...
May 20, 2012 - 10:21:39 AM
(HealthNewsDigest.com) - Continuing the old joke: Then you're built upside down. But, what can we say about olfaction—better known as the sense of smell?
As flavor and fragrance guru John C. Leffingwell, Ph.D puts it:
The sense of smell is a primal sense for humans as well as animals. From an evolutionary standpoint it is one of the most ancient of senses. Olfaction allows vertebrates and other organisms with olfactory receptors to identify food, mates, predators, and provides both sensual pleasure (the odor of flowers and perfume) as well as warnings of danger (e.g., spoiled food, chemical dangers). For both humans and animals, it is one of the important means by which our environment communicates with us.
In humans, the olfactory receptors are located deep within the nasal cavity, as part of the yellow-colored olfactory membrane, and occupy an area of around 0.39 square inches (2.5 square cm). Compare this to 1 full square yard (0.8 square meters) in a German Shepherd dog. That's well over 3000 times as much area! Plus, our canine friends also have 44 times as many receptor cells as we do, and devote much more of their brain to processing these signals.
For those who like SAT-style analogies, a dog's sense of smell is to ours, as our sense of reason is to theirs. Even so, based on the Nobel prize winning work of Richard Axel and Linda Buck, 1,000 genes—three percent of the human genome—code for olfactory receptor types.
Back in 1952, British biochemist John E. Amoore suggested that there are seven fundamental scents in play, although some researchers now believe that there are many more. These basic seven are:
- Pungent (like spices)
- Camphoraceous (like mothballs or muscle liniments)
- Ethereal (like dry-cleaning fluid)
- Putrid (like rotten eggs)
Many theories have been proffered as to how odors are interpreted. Leffingwell summarizes our current understanding of the matter, referring to it as a "combinatorial approach," much like how four nucleotides (adenine, cytosine, guanine and thymine) allow the creation of a nearly infinite number of genetic combinatorial sequences.
It appears that the sense of smell in mammals is based on a combinatorial approach to recognizing and processing odors. Instead of dedicating an individual odor receptor to a specific odor, the olfactory system uses an "alphabet" of receptors to create a specific smell response within the neurons of the brain. As in language (or music), the olfactory system appears to use combinations of receptors (analogous to words or musical notes, or to the way that computers process code) to greatly reduce the number of receptor types actually required to convey a broad range of odors.
Perhaps the most prevalent cinematic cliché involving olfaction portrays a recently widowed spouse smelling a garment worn by their departed loved one. As we have all experienced, scent is remarkably effective in conjuring up memories—usually emotional ones, including those long past. This phenomenon is known as involuntary memory, and is popularly called the Proust Effect, based on his novel In Search of Lost Time.
The most celebrated example of involuntary memory in that work is the "episode of the madeleine."
No sooner had the warm liquid mixed with the crumbs touched my palate than a shudder ran through me and I stopped, intent upon the extraordinary thing that was happening to me. An exquisite pleasure had invaded my senses, something isolated, detached, with no suggestion of its origin. And at once the vicissitudes of life had become indifferent to me, its disasters innocuous, its brevity illusory... Whence did it come? What did it mean? How could I seize and apprehend it? ... And suddenly the memory revealed itself. The taste was that of the little piece of madeleine which on Sunday mornings at Combray... my aunt Léonie used to give me, dipping it first in her own cup of tea or tisane. The sight of the little madeleine had recalled nothing to my mind before I tasted it. And all from my cup of tea.
A common, although not well-proven explanation for this phenomenon is that the olfactory system is located very close to the brain's centers of emotion (the amygdala) and memory (the hippocampus).
The practice of aromatherapy utilizes essential oils to promote physical, emotional, and spiritual health and balance. Various substances are specifically identified with physiological responses (e.g., eucalyptus relieves congestion, lavender promotes relaxation). While there are few rigorous studies confirming these effects, any contemporary practice that goes back thousands of years likely contains some merit.
But not all odors are pleasant. In fact, the control of unwanted odors is a serious concern of modern society.
A relatively new player in this space is OdorNo, an Ohio-based manufacturer of biodegradable odor barrier plastic bags. [http://www.odorno.com] The company's inaugural products have been created to contain the odor of diapers, incontinence products, and pet waste. Last month, I spoke with Garett Fortune, the firm's CEO.
OdorNo's motto is "Why smell it?" and its line of bags was developed in response to Garett's extreme sensitivity to foul odors. He claims that the bags work so well that even dogs can't smell material sealed inside them. While the bags provide a formidable barrier to odor, they are biodegradable, owing to a proprietary additive used in manufacturing. And yes, the bags are all manufactured in Ohio.
The products are currently available via the company's website, with plans in place to roll out both medical and retail distribution.
Michael D. Shaw
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