London, Jan 6 (IANS): The most common symptom of Covid-19 is losing sense of smell or taste 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.