Alongside a fever and a cough, one of the key symptoms of Covid-19 is losing the sense of smell. In some cases, it can be the only sign that there is anything wrong. And the problem can persist for months after the initial illness has passed.
Anosmia, as it is known medically, hits more than half of coronavirus patients, with most saying they’re also unable to taste anything. But when the senses begin to recover, there could be something even worse in store. Many are now reporting ‘phantom smells’ – the perception of scents that aren’t really there – and almost none of them is pleasant.
Some report a constant smell of cigarettes or rotting rubbish. Others say that familiar, comforting aromas such as fresh bread have become rancid and unbearable. The condition is called phantosmia, and doctors say the Covid-related symptoms of it are unlike anything they have seen before.
Alongside a fever and a cough, one of the key symptoms of Covid-19 is losing the sense of smell. In some cases, it can be the only sign that there is anything wrong (stock)
One sufferer, charity worker Karen Thomas from Berkshire, recovered from Covid-19 six months ago, and has been left with ‘nothing smelling like it used to’. ‘Perfume, aftershave and shower gel all smell like cleaning products’, says the 54 year-old.
The problem has affected her sense of taste, too. She says: ‘My favourite wine now tastes like sick, as do pineapple and soft cheeses.’
When Karen contracted Covid back in March at her father-in-law’s funeral, her sense of smell was the first thing to go – and food became bland and inedible.
In recent months her senses have returned – but with an odd twist.
She says: ‘I kept asking my husband if something was burning, and he would have no idea what I was talking about. Most recently, I’ve started smelling petrol.’
And she isn’t alone. A study of Covid symptoms in healthcare workers, soon to be published by the Global Consortium of Chemosensory Research, found that a third experience some level of phantosmia. For some this can just be a burning or cooling sensation in the nose, but for others the smells can be overwhelming.
WEIRD SCIENCE: Why Stone Age cannibalism was not the best source of protein
MEAT from chickens, cows and turkeys is a nutritious modern source of protein – but how does human flesh compare?
Researchers at the University of Brighton endeavoured to find out, to see how cannibalism rated as a diet during the Stone Age.
By analysing the calorie content of cadavers, the scientists found that a human weighing 65kg – or roughly ten stone – contains about 32,000 calories in their muscle tissue alone.
It might sound a lot, but it pales in comparison to other animals, such as cows, which have 360,000 calories in their muscle tissue, and deer, which contain roughly 163,000.
The results of the 2017 study indicated that our ancestors were unlikely to eat members of their own species, as the animals which they hunted at the time were of a much higher nutritional value – especially woolly mammoths, which had a belly-busting 3.6 million calories.
Most people will experience a loss of smell or taste from a cold at some point in their life. This is partly due to the mucus which forms, as well as swelling in the throat and nose blocking out odours. But viruses that affect smell can also damage small nerves in the nasal passage, causing a loss of sensation even after the virus leaves the body. As the nerves recover, some return to strength at different speeds from others, leading to a distortion in smell.
‘Phantosmia is very common in upper respiratory tract infections and it always begins with a loss of smell,’ says Professor Carl Philpott, of the Norwich Medical School.
He believes Covid-related phantosmia may be more severe because the virus damages taste buds, which work with receptors in the nose to form our complete sense of smell. He also points to early evidence that suggests Covid can affect areas in the brain linked to smell perception, leading to even more severe and long-lasting symptoms.
Anything with a scent emits a combination of molecules that stimulate various receptors in the nose, creating a unique pattern.
‘A rose, for example, has 13 smell molecules, which are picked up by different receptors,’ explains Prof Philpott. ‘But if only six of those smell receptors are functioning, a rose won’t smell like a rose.’
Prof Philpott says he now has patients in his clinic nearly every day complaining of phantom smells after suffering from Covid-19 – and some, like Susannah, have been suffering for more than six months.
Luckily there are treatments to speed up the recovery process, including a rehabilitation technique that Prof Philpott likens to physiotherapy for the nose.
Patients are sent jars containing paper imbued with distinctive scents – such as cloves, lemon, rose and eucalyptus – which they are instructed to smell twice a day. This helps stimulate the receptors, encouraging them to heal faster.
Prof Philpott says anyone suffering with phantosmia can also carry out their own training, by smelling familiar odours such as coffee. ‘It just has to be a smell you already know well,’ he adds.
While the coronavirus crisis has led to a rise of patients reporting phantom smells, Prof Philpott says it’s nothing new.
But this won’t be of any comfort to Karen, who is still mourning her loss of taste. She says: ‘I’ve lost two stone since this all began – everything tastes like cardboard.’