By Bethiel Dirar, Human Biology ’24

Author’s Note: I wrote this article as a New York Times-inspired piece in my UWP102B course, Writing in the Disciplines: Biological Sciences. Having chosen the topic of parosmia treatments as a writing focus for the class, I specifically discuss olfactory training in this article. In the midst of the pandemic, this condition caught my attention once I found out about it through social media. It had me wondering what it would be like to struggle to enjoy food post-COVID infection. I simply hope that readers learn something new from this article!

Ask someone who has had COVID-19 if they’ve had issues with their sense of smell, and they may very well say yes. According to the CDC, one of the most prevalent symptoms of the respiratory disease is loss of smell [1]. However, there is a lesser understood nasal problem unfolding due to COVID-19: parosmia. Parosmia, as described by the University of Utah, is a condition in which typically pleasant or at least neutral smelling foods become displeasing or repulsive to smell and taste [2].

As a result of this condition, the comforts and pleasures of having meals, snacks, and drinks disappear. Those who suffer from this condition have shared their experiences through TikTok. In one video that has amassed 9.1 million views, user @hannahbaked describes how parosmia has severely impacted her physical and mental health. She tearfully explains how water became disgusting to her, and discloses hair loss and a reliance on protein shakes as meal replacements. 

The good news, however, is that researchers have now identified a potential solution to this smelly situation that does not involve drugs or invasive procedures: this solution is olfactory training.
A new study shows that rehabilitation through olfactory training could allow patients with parosmia induced by COVID-19 to return to enjoying their food and drink. Olfactory training is a therapy in which pleasant scents are administered nasally [3].

Modified olfactory training was explored in a 2022 study as a possible treatment for COVID-19-induced parosmia. Aytug Altundag, MD and the other researchers of the study recruited 75 COVID-19 patients with parosmia from the Acibadem Taksim Hospital in Turkey and sorted them into two different groups. One group received modified olfactory training and another group served as a control and received no olfactory training [3]. Modified olfactory training differs from classical olfactory training (COT) in that it expands the number of scents used beyond COT’s four scents: rose, eucalyptus, lemon, and cloves [4 ]. These four scents were popularized in olfactory training use as they represent different categories of odor (floral, resinous, fruity, and spicy, respectively) [5].
For 36 weeks, the treatment group was exposed to a total of 12 scents twice a day that are far from foul. In each 12-week period, four scents were administered. For the first 12 weeks, they started with smelling eucalyptus, clove, lemon, and rose. During the next 12 weeks, the next set of scents were administered: menthol, thyme, tangerine, and jasmine. To round it off for the last 12 weeks, they smelled green tea, bergamot, rosemary, and gardenia scents. Throughout the study, the subjects would smell a scent for 10 seconds, then wait 10 seconds before smelling the next scent. The subjects completed the five minute training sessions around breakfast time and bedtime. [3]. 

To evaluate the results of the study, the researchers implemented a method known as the Sniffin’ Sticks test. This test combines an odor threshold test, odor discrimination test, and odor identification test, to form a TDI (threshold, discrimination, identification) score. According to the test, the higher the score is, the more normal the state of an individual’s olfactory perception is. A composite score between 30.3 and the maximum score of 48 indicates normal olfactory function while scores below 30.3 point to olfactory dysfunction [3].

The results of this research are promising. By the ninth month of the study, a statistically significant difference in average TDI scores had been found between the group that received modified olfactory training and the control group (27.9 versus 14) [3]. This has led the researchers to believe that with prolonged periods of the therapy, olfactory training could soon become a proven treatment for COVID-19-induced parosmia. 

With this conclusion, there is greater hope now for those living with this smell distortion. Fifth Sense, a UK charity focusing on smell and taste disorders, has spotlighted stories emphasizing the need for effective treatments for parosmia. One member of the Fifth Sense community and sufferer of parosmia, 24-year-old Abbie, discussed the struggles of dealing with displeasing odors. “I ended up losing over a stone in weight very quickly because I was skipping meals, as trying to find food that I could eat became increasingly challenging,” she recounted to Fifth Sense [6].

If olfactory training becomes an effective treatment option, eating and drinking might no longer be a battle for those with parosmia. Countless people suffering from the condition will finally experience an improvement in their quality of life so desperately needed, especially with COVID becoming endemic.

REFERENCES:

1. Centers for Disease Control and Prevention. Symptoms of COVID-19. Accessed November 20, 2022. Available from: https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symptoms.html
2. University of Utah Office of Public Affairs. Parosmia after COVID-19: What Is It and How Long Will It Last? Accessed November 20, 2022. Available from: https://healthcare.utah.edu/healthfeed/postings/2021/09/parosmia.php
3. Altundag Aytug, Yilmaz Eren, Caner Kesimli, Mustafa. 2022. Modified Olfactory Training Is an Effective Treatment Method for COVID-19 Induced Parosmia. The Laryngoscope [Internet]. 132(7):1433-1438. doi:10.1002/lary.30101
4. Yaylacı Atılay, Azak Emel, Önal Alperen, Ruhi Aktürk Doğukaan, and Karadenizli Aynur. 2022. Effects of classical olfactory training in patients with COVID-19-related persistent loss of smell. EUFOS [Internet]. 280(2): 757–763. doi:10.1007/s00405-022-07570-w
5. AbScent. Rose, lemon, clove and eucalyptus. Accessed February 5, 2023. Available from: https://abscent.org/insights-blog/blog/rose-lemon-clove-and-eucalyptus 
6. Fifth Sense. Abbie’s Story: Parosmia Following COVID-19 and Tips to Manage It. Accessed November 23, 2022. Available from: https://www.fifthsense.org.uk/stories/abbies-story-covid-19-induced-parosmia-and-tips-to-manage-it/