Why does that smell make me happy?  or sad 🙁

Here are some facts you may or may not know about your sense of smell:

  • “Taste” is mainly dependent (80%) on smell.  If you eat something while pinching your nose, you will not get the full “taste”.  The only tastes that persist without smell are sweet, salty, sour, bitter and umami, which is the savory sensation (Scienceworld.ca)
  • “Aromatherapy” was invented in the 1920’s by French chemist Rene-Maurice Gattefosse to describe the use of naturally fragrant essential oils to treat injury and disease. (study)
  • Essential oils contain terpenes, which are actually VOCs (volatile organic compounds) and aromatic compounds. 
  • When we are hungry, our sense of smell gets stronger.
  • Injuries to the nose risk damage to the plate of bone that separates the olfactory receptor cells in the nose from the olfactory bulb in the brain.  If these are severed, then you can become anosmic–with no sense of smell. 
  • Smell loss is associated with Parkinson’s and Alzheimer’s diseases, among others, and diminishing sense of smell can be an early sign of onset of these conditions. 
  • The sense of smell is developed even before we are born, in our mothers’ wombs.  It continues to strengthen through the first 8-10 years of life.  

“Fragrances directly and/or indirectly affect the psychological and physiological conditions of humans”, according to Meta Analysis study.  These physiological changes can be measured in EEG (electroencephalograph) signals made by brain waves, heart rate, and temperature…but they can also be measured in task performance, such as the way peppermint odor significantly increases strength tasks such as running speed, grip strength and number of pushups.(article here)  Perhaps most well-known is the connection between lavender, drowsiness and deep sleep, but did you know that inhalation of eucalyptus oil significantly decreases pain and blood pressure after surgery?(free article)  These are just a few of the effects of dozens of fragrances which have been studied.

Despite these measured physiological effects, there are also learned (experiential) effects of fragrance which cause an emotional response.  For example, the smell of formaldehyde, while poisonous in its own right, is associated with death and unpleasant conditions by many because of its presence in science labs as the preservation fluid for dissection animals.  Thus, just traces of formaldehyde are repulsive to many.  Likewise, flowers can evoke warm memories from childhood if they have the same fragrance notes of mom’s favorite perfume.  The connection between fragrance and memories stems from shared centers of smell processing and emotion in the brain: after they are received as electrical signals in the olfactory bulb in the front of the brain, fragrance information is sent to the limbic system, including the amygdala and the hippocampus, the regions related to emotion and memory (The Harvard Gazette).

Two interesting experiments show how the same scent can elicit very different responses in different populations.  They both asked participants to rate a list of common odors, however, one study was conducted in Great Britain (mid-1960’s) and one study was conducted in the US (late 1970’s).  Both contained the scent of wintergreen, which was rated as very unpleasant by Britons, and highly pleasant by Americans.  Why the difference?  It is due to memories associated with wintergreen.  This flavor and its corresponding scent was used in medicines during the WWII era in Europe, which naturally evoked unpleasant memories.  In the US, however, wintergreen is typically used in candies (which is exactly why I like it). 

Unfortunately, fragrances can also be poisonous to those with Multiple Chemical Sensitivity (MCS).  People who suffer from MCS can become ill with even small traces of fragrance, although according to an 840 page report (summarized) by Quebec’s public health agency, the condition is more of an anxiety disorder brought on by anticipation of chemical exposure.  Following this conclusion then leads us to consider whether it is the memory of negative experiences that cause the symptoms, rather than the VOCs in the fragrance associated with the experience. 

Now that you know the reason for your emotions when you discern a certain smell, check out our post about de-scenting and scenting your home (Ewww! How can I get rid of that smell?).