When the Nose Doesn’t Know

When the Nose Doesn’t Know. A lady smelling a flower

Did COVID-19 disrupt the sense of smell? Coronavirus is not the only virus that affects the ability to smell, but it is unique in the way in which it does so. As an example, the common cold causes an inflammatory response in the nose, and mucus builds up which reduces our ability to smell.  The unique aspect of COVID-19 is that the virus actually crosses the blood-brain barrier and gets into the nervous system, thus affecting the sense of smell and taste.

In a study published in the Journal of Internal Medicine, researchers found that 86% of people with a mild case of coronavirus lost their sense of taste and smell.  The study involved more than 2,500 patients across 18 European hospitals. According to the researchers, 75% to 85% of people regained their ability to taste and smell about two months after their infection, while 95% of the people regained the ability to taste and smell at six months.

When coronavirus-related, olfactory dysfunction improves spontaneously, specific treatment may not be required.  According to Katherine Lisa Whitcroft, BSc, MBChB at the Smell and Taste Clinic of the Technical University of Dresden in Germany, if loss of smell persists beyond 2 weeks, treatment may be considered. Olfactory training involves repeat and deliberate sniffing of a set of odorants (cloves, lemons, rose, and eucalyptus) for 20 seconds each at least twice a day up to three months or longer.

Even though anyone can do smell training, people should visit their doctor to determine if they have a problem with their sense of smell.

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Whitcroft KL, Hummel T. Olfactory Dysfunction in COVID-19: Diagnosis and Management. JAMA. 2020;323(24):2512–2514. doi:10.1001/jama.2020.8391

Rhea, E.M., Logsdon, A.F., Hansen, K.M. et al. The S1 protein of SARS-CoV-2 crosses the blood–brain barrier in mice. Nat Neurosci 24, 368–378 (2021). https://doi.org/10.1038/s41593-020-00771-8

Leichein, J., Chiesa-Estomba, C. et al, Prevalence and 6-month recovery of olfactory dysfunction: a multicentre study of 1363 COVID-19 patients. Journal of Internal Medicine. https://doi.org/10.1111/joim.13209