Hi my name is Catherine and I am a “fragrance holic.”

There, I said it.

What’s your olfactory prowess? Mine, apparently quite good. Here’s the thing, I perceive smells everywhere, which speaks to an acute sense of smell, at least, I think so. I became aware of my “gift” or  curse — as it were–as an adolescent. That’s when I noticed that smells were apparently more poignant to me than they were to my peers. I also took pleasure in smelling a number of…well, quite frankly, stuff. I would often go about sniffing the wild flowers and other vegetation that grew along the many unbeaten paths of my childhood adventures.  That’s not unusual. But, this next one might trigger a minor head scratch; I also enjoyed (maybe still do) the smell of my pillow; not the residual smell of the blue soap that was used to do the laundry, but the deep, integral smell of whatever was hidden in its filling to the extent that I would sink my face hard into it and  inhale. I also find the aroma after the rain strangely captivating (that’s call petrichor by the way), and the smell of the ocean, clean water, book pages, and steel wool. Not surprisingly, I am a huge fan of fragrances, not so much perfumes, but plugins, car fresheners, waxes, essential oil diffusers, potpourri, and most recently sprinkles by Pink Zebra. My daughter sometimes jokes that my nostrils will get all messed up some day. Maybe so, but for now I enjoy the good and the bad. On the other end of the spectrum, smells that I find repugnant are generally unbearable(insert Dominican: mwen lay mor). Death, if only ephemerally, looks good then. Among those god-forsaken smells are the those of a gym on a sweltering summer day, sweaty feet(sometimes you can’t escape those if you partner is so inflicted), a multi-stall public restroom right after a dump(I’m keeping it 100), Lubbock, Texas summers’ easterly breeze,  and a classroom of middle schoolers  at 2:00 pm (What? Too real?). Now, when you find yourself in such a situation, you could  hold your breath, then scurry away from the offender as quickly as you can, or breathe ever so shallowly and pray that the molecules don’t get to those darn receptors somewhere up your nose. Over the years, I’ve often wondered about scents and smelling. What follows is more than you ever care to know about the topic in my neurotic quest to understand more about “smelling.”

Human Olfaction

Humans are generally are considered poor  “smellers” especially when compared to other members of the class, Mammalia. At least this used to be the case. From an evolutionary perspective, in fact, we have experienced diminished sense of smell, as our visual acuity increased. At one time, it was believed that humans were only able to distinguish among 10 thousand odors. However, a recent study by Bushdid and colleagues (2014),  determined that humans can discriminate at least 1 trillion olfactory stimuli, much more than was previously believed. One study by Castro, Ramanathan,  and Chennubhotla (2013) reduced this to 10 basic categories:

1. Fragrant (including your florals, sweet, and perfumery)
2. Woody, resinous
3. Fruity, other than citrus
4. Chemical (paint, alcohol,gasoline)
5. Minty, peppermint (eucalyptus, spicy)
6. Sweet (vanilla, chocolate, almond)
7. Popcorn(burnt, smoky)
8. Lemon (fruity, citrus)
9. Sickening (putrid, foul, decayed)
10. Sharp/pungent

Another study published in Psychological Science journal suggested that we can smell fear and disgust through the chemosignals that these emotions emanate! In more cutting edge research (I’m talking artificial smell type edge ), Lee and his research team mimicked the human smell sensing mechanism  with an nanobioelectronic nose (nbe-nose).  The mechanical nose was able to “smell” gases at a concentration as low as 0.02 parts-per-trillion (ppt), which was comparable to a highly trained, human expert’s nose!

How Do We Smell?

The process of smell begins at the back of the nose.We are able to smell because of sensory receptors that respond to chemicals in the air. In humans, these chemoreceptors are located in the olfactory epithelium — a patch of tissue about the size of a postage stamp located high in the nasal cavity. The tips of these cells contain  about 450 different types of receptors that bind odor molecules that float past. Each receptor can be “turned on” by many different odor molecules, which in turn can “turn on” several different types of receptors. Not all receptor – odorant interaction are created equal. Some are better  “fits” than others. This complexity is what allows us to detect a wide array of smells. Finally,  neurotransmitters carry the smell signal to the brain.

Will you be able to distinguish among the seven odors commonly used by neurologists?- baby powder, chocolate, cinnamon, coffee, mothballs, peanut butter, and soap. Some anosmics can’t identify any!

Smell and Health

Findings from one 2014 study of a nationally representative sample of older U.S. adults by Pinto and colleagues found that olfactory function  is a strong predictor of 5-year mortality. The authors concluded that decline in the sense of smell might predict death in five years. Yikes!

Smell Facts

• The inability to smell is  called anosmia.
• Our ability to distinguish among common odorants decreases drastically between age 20 and 70.
• African-Americans and Hispanics experience  age related loss of smelling earlier than Whites.
• Scent cells are renewed every 30 to 60 days.
• 1 in 10 people are unable to detect the chemical added to natural gas to aid in its detection from leaks.
• Our ability to smell  is better in the spring and summer, due to the additional moisture in the air.
• Women have a better sense of smell than men.
• The olfactory nerve is the only cranial nerve directly exposed to the environment.
• Some hotel chains have devised their own smell.
• The sense of smell is the first of all our senses to develop.
• People who suffer from cacosmia perceive all smells as something revolting.
• Like a fingerprint we each have a unique odor.
• Smell has a powerful link to memory.

And as if you care to know:

• 1 person in 1000 is insensitive to the foul-smelling odorant released by skunks.

I get to this much needed conclusion with this quote that I really love!

“I’m barely human. I’m more like a creature; to me, everything gives off a scent! Thoughts, moments, feelings, movements, words left unsaid, words barely spoken; they all have a distinct sense, distinct fragrances! Both a smell and a touch! To inhale is to capture, to experience! I can perceive and I can “touch” in so many odd ways! And so I am made up of all these scents, all these feelings! An illumination of nerve endings!”
― C. JoyBell C.

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References

1. Bushdid, C., Magnasco, M. O., Vosshall, L. B., & Keller, A. (2014). Humans Can Discriminate More than 1 Trillion Olfactory Stimuli.Science, 343(6177), 1370-1372.
2. Castro,  J. B., Ramanathan, A., & Chennubhotla, C. S. (2013) Categorical Dimensions of Human Odor Descriptor Space Revealed by Non-Negative Matrix Factorization. PLoS ONE 8(9): e73289. doi:10.1371/journal.pone.0073289
3. de Groot, J. B., Smeets, M. M., Kaldewaij, A., Duijndam, M. A., & Semin, G. R. (2012). Chemosignals Communicate Human Emotions. Psychological Science (Sage Publications Inc.), 23(11), 1417-1424. doi:10.1177/0956797612
4. Lee, S. H., Kwon, O. S., Song, H. S., Park, S. J., Sung, J. H., Jang, J., & Park, T. H. (2012). Mimicking the human smell sensing mechanism with an artificial nose platform. Biomaterials, 33(6), 1722-1729. doi:10.1016/j.biomaterials.2011.11.044
5. Pinto,  J. M., Wroblewski, K. E , Kern, D. W., Schumm, L. P.,  & McClintock, M. K (2014). Olfactory Dysfunction Predicts 5-Year Mortality in Older Adults. PLoS ONE 9(10): e107541. doi:10.1371/journal.pone.0107541
6. Shepherd, G. M. (2004). The Human Sense of Smell: Are We Better Than We Think?. Plos Biology, 2(5), 572-575.