Olfactory dysfunction: It takes 21 days to recover from smell, taste loss in Covid
The most common symptom of Covid-19 is losing the sense of smell or taste commonly known as olfactory dysfunction and a new study suggests that it takes around 21.6 days to recover from the symptoms in mild cases.
The reduced or distorted ability to smell during sniffing or eating is also known as olfactory dysfunction.
According to the study, published in the Journal of Internal Medicine, the patient-reported prevalence of olfactory dysfunction was 85.9 per cent in mild cases of COVID-19.
And 4.5 per cent in moderate cases and 6.9 per cent in severe-to-critical cases.
"Olfactory dysfunction is more prevalent in mild Covid-19 forms than in moderate-to-critical forms, and 95 per cent of patients recover their sense of smell at 6-months post-infection," said lead author Jerome R. Lechien of Paris Saclay University.
To determine the results, the researchers involved 2,581 patients from 18 European hospitals.
The team also found that the average duration of olfactory dysfunction reported by patients was 21.6 days, but nearly one-quarter of affected patients reported that they did not recover their sense of smell 60 days after losing it.
Objective clinical evaluations identified olfactory dysfunction in 54.7 per cent of mild cases of COVID-19 and 36.6 per cent of moderate-to-critical cases of COVID-19. At 60 days and 6 months, 15.3 per cent and 4.7 per cent of these patients did not objectively recover their sense of smell, respectively.
Reports of Covid-19-related olfactory dysfunction describe a sudden onset of olfactory impairment, which may be in the presence or absence of other symptoms.
Up to 80% of people who test positive for COVID-19 have subjective complaints of smell or taste loss. That percentage rises when these patients are tested using objective methods that measure smell function. Most patients first notice problems with their sense of smell, but because the smell is necessary to taste the flavor, the symptoms are often connected.
One possibility is that people with upper respiratory infections often have congestion, drainage, and other nasal symptoms that can block odor's ability to reach the smell nerve, which sits at the top of the nasal cavity. But, we believe the primary cause, particularly for people with extended or permanent loss of smell function, is that the virus causes an inflammatory reaction inside the nose that can lead to a loss of the olfactory, or smell, neurons.
In some cases, this is permanent, but in other cases, the neurons can regenerate. That's likely what determines which patients recover. In COVID-19, we believe smell loss is so prevalent because the receptors for COVID-19 that are expressed in human tissue are most commonly expressed in the nasal cavity and in the supporting cells of the olfactory tissue. These supporting cells surround the smell neurons and allow them to survive.
