The majority of society knows the term for the loss of sight or the loss of hearing, but what about the loss of smell or taste?  Well this week (18^th May 2020), the term ‘anosmia’ hit the national press as it became recognised as one of the three main symptoms of COVID-19.  This blog describes what anosmia is, and why the power of smell should never be underestimated. 

Anosmia is the term used to describe the loss of the ability to smell.  There are many other derivatives of the term, including hyposmia (a reduced sense of smell), hyperosmia (an increased sense of smell) and dysosmia (errors such as smelling things differently (parosmia) or things that are not there (phantosmia)).  I could go on, but the point is that there are many ways in which our sense of smell can be impaired.   

The loss of taste is called ageusia (with similar derivatives as described above; hypogeusia, dysgeusia, etc.).  This condition is related to impaired function of the tongue, however, our perception of taste is a combination of gustation (the sense of taste from the tongue) and olfaction (the sense of smell).  Research articles have estimated that our perception of taste is between 75% and 95% smell based, and while there is rarely evidence given to support those claims (see here for a report discussing just this), it is generally accepted that olfaction plays a dominant role.  As a result, a loss of the ability to smell, anosmia, has a large impact on our ability to taste, even if the tongue is functioning well. 

There are various causes of anosmia.  The most common of which is merely a result of the smell molecules not being able to reach the olfactory receptors (the smell sensors) due to some kind of obstruction, like nasal congestion.  Other common causes are infection/disease (from a huge variety of bacteria and viruses, but including COVID-19), post-infection disorders, physical damage and aging.  In rare cases, anosmia can even be congenital (present from birth), for which there is currently no treatment. 

So we have begun to establish what anosmia is, but does it really matter?  Some people can’t smell flowers or fully taste their dinner, but so what, you might ask.  Much of my current research explores how our behaviour and thinking can be modified through the use of smell, but here I will focus on the consequence of not having that sense. 

For a single bout of short-term anosmia, it would be reasonable to view it as mild annoyance.  In the current pandemic, the loss of smell may also cause elevated anxiety due to its link with the COVID-19 virus.  However, the longer term consequence of anosmia can be far-reaching and severe.  The sense of smell provides a connection with the environment, and without that there is a psychological disconnection.  There is a growing body of literature that has explored the psychological links between olfaction, memory and emotion, but those are severed with anosmia.  For example, you may have had the experience of a certain smell reminding you of a past event.  Without those prompts, some memories remain unaccessed.  Likewise there may be fragrances that relax you or make you happy, and those links are also cut.  Other connections might include family meals, where all food and drink are bland or tasteless (the main problem for many sufferers), walks in the countryside cannot be experienced in the same way, or perfumes of partners are meaningless.  Furthermore, harmful odours such as from gas leaks, burning, or spoilt food are not detected, not even an awareness of possible body odour. 

The quality of life of those affected by anosmia is significantly degraded, with worrying effects on psychological well-being.  In 2013, the charity Fifth Sense asked 496 people with anosmia about their experience with the condition (a summary can be found here), and they report feelings of loneliness, fear, anger and even depression as a result.  It can lead to difficulties with social relationships, weight loss, and changes what activities they choose to take part in.  Multiple research papers corroborate and bolster these findings (see reading list below).

It is estimated that between 3% and 20% of the population have either anosmia or hyposmia.  It is a silent condition that negatively impacts everyday life, yet many are unaware it even has a name.  As with the majority of olfactory research, our knowledge and understanding of the psychological impact of anosmia is underdeveloped.  However, wider awareness of the condition and the profound effect it can have is growing, and with just cause. 

In addition to the links in the text, please find some links for further reading:

Large charity with great knowledge and easy to explore website:
https://www.fifthsense.org.uk/smell-disorders/ or https://www.facebook.com/FifthSenseUK/

Personal experiences of someone with anosmia:
https://girlwhocantsmell.com/ or https://www.facebook.com/girlwhocantsmell/

For more in-depth research papers, see:

Clinical review of anosmia:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5863566/pdf/bjx025.pdf

Further detail on anosmia and dysgeusia:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2579627/