Sense of Smell
Why is an eye doctor writing about our sense of smell?? Because it is fascinating! Smell is an under-rated and under-appreciated sense in humans. People can easily imagine how devastating it would be to lose our vision, but we tend to think that losing our sense of smell would have little impact on our lives. In fact, a survey of young people indicated that most would rather lose their sense of smell than live without their smartphones!
Covid-19 has brought new attention to a condition called anosmia – the loss of smell. Anosmia is a common symptom of COVID-19 – up to 86% of people infected with the virus may partially or fully lose their sense of smell. Anosmia can be the first or only symptom of mild COVID-19 infection. Most people recover their sense of smell within days or weeks, but a small percentage of people are experiencing long-term losses.
When we stop to appreciate it, our sense of smell is wondrous. Our sense of smell enhances and broadens our taste and appreciation of food. But think too of the information that smell gives us… we can deduce that a lawn has been mowed just from the whiff of fresh-cut grass, or know that bread has been baked the moment you open your front door. Smell also provides essential information on dangers in our environment – the smell of smoke, gas leaks, or rancid food. Humans can even distinguish between the smells of sweat from exercise versus sweat from fear. We gain all this information almost instantly from breathing in some chemical molecules floating on airwaves – it is amazing!
Our visual system has been well studied and we know a lot about the structure and function of the photoreceptors (rods and cones) that provide us with sight. Our smell receptor cells (olfactory sensory neurons) were only discovered in the 1990’s, and there is a great deal to be learned about them. Viruses have been known to affect our sense of smell, but it was previously assumed that this was due to congestion in the nasal passages. With COVID-19, many patients with anosmia have no nasal congestion to account for their loss of smell. Researchers are now thinking that the COVID-19 virus may cause damage to the supporting cells to the olfactory sensory neurons, which in turn causes a loss of function of the actual nerves responsible for smell.
As this pandemic continues, please be alert to any changes to your sense of smell. A loss of smell and/or taste indicates a need to get COVID tested and isolate while awaiting results. So take a moment today to appreciate your amazing sense of smell (and don’t forget your vision too! – book an appointment for an eye examination if it’s been more than two years).
Dr. Lisa Scharf