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Cochrane ENT at the Nuffield Department of Surgical Sciences has published two systematic reviews investigating the effectiveness and safety of interventions to prevent and treat loss of smell following COVID-19 infection.

Woman smelling the scent from an open bottle

Loss of sense of smell is a frequent symptom following COVID-19 infection. Although for a significant proportion of patients, the loss is only temporary and their sense of smell recovers relatively quickly, for others, the problem can persist and can have a major impact on quality of life.

The Cochrane reviews highlight the current uncertainty about the treatments and the ways to prevent lasting problems with sense of smell after COVID-19 infection.

The first review, 'Interventions for the treatment of persistent smell disorders (olfactory dysfunction) after COVID-19 infection' involved one study with 18 people with problems with their sense of smell that started after a COVID-19 infection and lasted a least four weeks. It compared steroid tablets plus a nasal spray (consisting of a mix of steroids, decongestant and an agent that breaks down mucus) with no treatment.

Researchers at Cochrane ENT identified that the potential benefits and harms of treatments for problems with sense of smell (reduced, changed or lost sense of smell) that last weeks or months after COVID-19 are very uncertain.

The second review, 'Interventions for the prevention of persistent smell disorders (olfactory dysfunction) after COVID-19 infection', involved one study with 100 people with problems with their sense of smell that started after a COVID-19 infection and had lasted less than four weeks at the start of the study. It compared a steroid spray that goes into the nose with no treatment. Everyone taking part in the study was asked to spend a short time each day practising smelling particular scents, to try and stimulate their sense of smell to return. 

The team discovered that the potential benefits and harms of interventions to prevent problems with sense of smell (reduced, changed or lost sense of smell) that last weeks or months after COVID-19 are also very uncertain.

These are living systematic reviews, which will include new evidence as it becomes available. 


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