Researchers are calling for people struggling to regain their sense of smell after falling ill with Covid-19 to undergo "smell training" rather than being treated with steroids.

This is a process that involves sniffing different odours over a period of months to retrain the brain to recognise different smells.

A group of international experts say smell training is cheap and simple.

And unlike steroids, it is free from potential side effects.

A loss of smell is one of the main symptoms of coronavirus infection, along with a fever and a persistent cough.

In most cases, loss of smell will return relatively quickly after the illness has passed.

But around one in five people report they are still having problems eight weeks after falling ill.

One treatment that has been prescribed by doctors is a course of drugs known as corticosteroids, which lower inflammation in the body and are already used to treat conditions such as asthma.

But Prof Carl Philpott, from the University of East Anglia's Norwich Medical School, who was part of the team reviewing current evidence, said there was very little to suggest that corticosteroids would help with smell loss.

"And because they have well-known potential adverse side effects, our advice is that they should not be prescribed as a treatment for post-viral smell loss," he said.

"Luckily most people who experience smell loss as a result of Covid-19 will regain their sense of smell spontaneously."

The steroids' side effects include fluid retention, high blood pressure, and problems with mood swings and behaviour.

Instead, in a paper published in the journal International Forum of Allergy & Rhinology, the researchers suggest "smell training".

This involves sniffing four things that have a distinctive, easily identifiable and familiar smell - for example, oranges, mint, garlic or coffee - twice a day for several months.

Prof Philpott said research shows that 90% of people fully recover their sense of smell after six months.

If it doesn't return, he says "smell training" helps to retrain the brain's smell pathways to recognise different odours.

"It aims to help recovery based on neuroplasticity - the brain's ability to reorganise itself to compensate for a change or injury," he said.

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