Post-COVID-19 Parosmia

It is estimated that 86% of people diagnosed with COVID-19 lose some or all of their ability to smell. Olfactory dysfunction is typically more common in milder cases of COVID-19, even though it is the result of nerve damage (Lechien et al., 2021). The majority of patients suffering an altered sense of smell typically see improvement within three weeks. Unfortunately, about 25% of patients report their sense of smell showing no improvement after 60 days.

The mechanism for how COVID-19 infection can result in olfactory dysfunction is not fully understood at this time. In other parts of the body, we know that SARS-CoV-2 gains entry into the cell by attaching to ACE2 and TMPRSS2 receptors on the surface of cells. Olfactory sensory neurons do not express ACE2 on their surfaces. However, ACE2 and TMPRSS2 are expressed in sustentacular cells of the olfactory epithelium. This suggests that sustentacular cells are involved in COVID-19 viral entry into cells of the olfactory epithelium and gives insight into how olfactory impairment occurs with such infections (Bilinska et al., 2020).

Many young patients who have recovered from COVID-19 infections are reporting parosmia, sometimes lasting months after the initial infection. Parosmia is a term used to describe a distorted sense of smell resulting from a health condition. Like impaired or absent sense of smell common with COVID-19 infections, parosmia is also the result of olfactory damage. The olfactory bulbs underneath the front of the brain receive signals from olfactory neurons. Damage to olfactory neurons alters the way smell signals reach the brain (Duyan et al., 2021).

Parosmia in post-COVID-19 patients has been described as scents that were once pleasant, now smell bad or rotten. Some patients have reported every odour they can smell smells like gasoline, metal, ammonia, or garbage. Since smell and taste are closely linked, parosmia can have negative consequences on a patient’s relationship with food. It is common for patients to report weight loss driven by difficulty eating, as for some patients, food smells and tastes rancid.

Patients with parosmia often also experienced loss of smell and taste while they were sick with COVID-19. A recent study has shown that of 268 participants experiencing parosmia post-COVID-19 infection, 70.1% of them were age 30 or younger, and 73.5% were female (Rashid et al., 2021).

A survey in June 2021 found that out of 1299 participants, 140 of them (10.8%) reported having parosmia post-COVID-19. About half reported a sudden onset, while the remainder reported a gradual onset. The five most common types of food that triggered parosmia were meat, onions, eggs, garlic, and rice. This condition typically lasts between 9 days and 6 months, and the average duration is 3.4 months. In this study, 50.7% of patients reported their parosmia lasting for longer than three months (Raad et al., 2021)

Reddot Biotech is proud to support the research of COVID-19 and COVID-19 long-haul disorders. Browse our COVID-19 related products here!

If you or a loved one are suffering from parosmia, please know you are not alone. The AbScent Network offers a welcoming online community for anyone suffering post-COVID-19 parosmia. View their webpage here. 

References:

Bilinska, K., Jakubowska, P., Von Bartheld, C. S., & Butowt, R. (2020). Expression of the SARS-COV-2 entry proteins, ACE2 and TMPRSS2, in cells of the olfactory epithelium: Identification of cell types and trends with age. ACS Chemical Neuroscience, 11(11), 1555–1562. https://doi.org/10.1021/acschemneuro.0c00210

Duyan, M., Ozturan, I. U., & Altas, M. (2021). Delayed parosmia following SARS-COV-2 infection: A rare late complication of COVID-19. SN Comprehensive Clinical Medicine, 3(5), 1200–1202. https://doi.org/10.1007/s42399...

Lechien, J. R., Chiesa‐Estomba, C. M., Beckers, E., Mustin, V., Ducarme, M., Journe, F., Marchant, A., Jouffe, L., Barillari, M. R., Cammaroto, G., Circiu, M. P., Hans, S., & Saussez, S. (2021). Prevalence and 6‐month recovery of olfactory dysfunction: A multicentre study of 1363 COVID‐19 patients. Journal of Internal Medicine, 290(2), 451–461. https://doi.org/10.1111/joim.1...

Raad, N., Ghorbani, J., Safavi Naeini, A., Tajik, N., & Karimi‐Galougahi, M. (2021). Parosmia in patients with COVID‐19 and olfactory dysfunction. International Forum of Allergy & Rhinology, 11(10), 1497–1500. https://doi.org/10.1002/alr.22...

Rashid, R. A., Alaqeedy, A. A., & Al-Ani, R. M. (2021). Parosmia due to covid-19 disease: A 268 case series. Indian Journal of Otolaryngology and Head & Neck Surgery. https://doi.org/10.1007/s12070...