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Anosmia in COVID infection

Dr Roger Henderson
Reviewed by Roger HendersonReviewed on 29.04.2024 | 3 minutes read
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Anosmia is a condition that describes failure of our sense of smell. Although there are many other conditions that can cause anosmia, it has become well-known since the pandemic started, as it was classified as one of three typical symptoms of COVID-19 before people were vaccinated.

Loss of sense of smell occurs during the acute COVID illness but can last long after you have since recovered. Your ability to smell is closely linked to your taste buds so it can make your food taste bland or alter your smell so that things either don’t smell of anything or smell very different. You may detect a charred or burning smell, and can have a knock-on effect on your appetite.

You may only be able to smell or taste a little – partial anosmia – or you may find certain smells or tastes unpleasant. You may experience a bad smell all the time, like smelling smoke or petrol, even if it’s not present.

How does it happen?

Uniquely unlike most other viruses that cause nasal congestion or inflammation, COVID-19 crosses the blood-brain barrier entering the nervous system and affecting the neural connections that detect and process smells, known as your olfactory system.

How long will the anosmia last?

COVID-19 affects everybody differently, it is therefore difficult to predict how long anosmia may affect you. As a general rule it appears that 90% of people with COVID-related anosmia can expect a substantial improvement in their sense of smell within 4 weeks of their infection. Others can take several months or even longer to return and for a small number their sense of smell may not return – however, recent studies suggest that persistent COVID-19 related anosmia has an excellent prognosis with nearly complete recovery at 1 year for most people.

Many find they experience distorted smells as the sense returns, or imagine smells that aren’t there, a phenomenon known as phantosmia or olfactory hallucination, which can be distressing if they are unpleasant smells, but it’s a sign of the nerves regenerating and usually settles over time.

How can I get my sense of smell back?

The majority of people will gradually regain their smell. Research shows that 90% of people fully recover, but it can take up to 18 months to regenerate olfactory cells, depending on where in the olfactory system the virus has damaged, and for some, it will unfortunately be permanent damage.

Research is ongoing as to whether surgical techniques may prove effective. In the meantime, the mainstay of treatment is smell retraining therapy, a short course of steroid tablets (although these should not be used during the initial COVID-19 infection), or a steroid nasal spray that your doctor can prescribe. The retraining therapy has had reasonable results, but there is mixed success with the other methods.

Smell retraining therapy works by slowly reintroducing yourself to distinct smells, in the hope that it can stimulate the olfactory system in the brain to remember how to smell. The four categories that are advised to retrain are floral, such as rose, fruity, like orange, spicy, like cloves, and a category called resinous, which eucalyptus fits into.

The retraining technique involves taking gentle sniffs of each scent in order, for 20 seconds at a time, twice a day, and concentrating on the memory of that smell. This should be done for at least 3 months.

Is there any support available?

Support is available from charities such as Fifth Sense (www.Fifthsense.org.uk) and AbScent (www.abscent.org).

There are safety implications, if you can't smell burning or gas leaks, so make sure you have smoke alarms at home and work, and test them regularly. If you have gas hobs, buy some gas sensors in case there's a leak. Ensure household members and co-workers are aware that you will not be able to smell any danger, so they can be more vigilant.

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Dr Roger Henderson
Reviewed by Roger Henderson
Reviewed on 29.04.2024
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