'Smell training' could help people who have experienced unusual odour distortions after contracting Covid-19, to smell normally again.

Researchers from the University of East Anglia have been investigating parosmia - a symptom where people experience strange and often unpleasant smell distortions.

Instead of smelling a lemon, people may smell rotting cabbage, or chocolate may smell like petrol.

The symptom has been linked to smell disturbance in Covid-19, as well as due to other viruses and head injuries.

Prof Carl Philpott from UEA’s Norwich Medical School, said: "We know the pandemic is leaving many people with long-term smell loss, or smell distortions such as parosmia – this may now be as many as 90,000 people in the UK.

“For people with parosmia, the smell of certain things – or sometimes everything – is different, and often unpleasant. So for example, someone with parosmia could sniff at a cinnamon stick, but to them it would smell like something horrible – perhaps rotten food, or worse.

“Smell training involves sniffing at least four different odours twice a day every day for several months. It has emerged as a simple and side-effect free treatment option for various causes of smell loss."

A research team worked with 143 people who had experienced a loss or change in their sense of smell due to post viral infection.

The participants received a variety of smell training kits – consisting of different odours, including eucalyptus, lemon, rose, cinnamon, chocolate, coffee, lavender, honey, strawberry and thyme.

They were tested for how well they could smell different odours at the start of the trial, and after six months of smell training.

Prof Philpott said: “We found the presence of parosmia and worse smell performance on testing of odour identification and discrimination was associated with clinically significant recovery in smell function for people experiencing post-viral smell disorders.

“This means smell training can help the smell pathways to start to regenerate and recover."

The research was carried out before Covid-19, however researchers say their findings could be helpful to people who lost their sense of smell as a result of the pandemic.