If you wake up feeling otherwise fine but without your sense of smell, could that be a sign you’ve been infected with coronavirus?
Yes, say the experts, but it’s worth noting COVID-19 isn’t the only thing that can affect your olfactory system.
“With the pandemic currently going on, if you are young or old and have an unexplained smell loss come on quite quickly, even in the setting of minimal respiratory symptoms, you should be highly suspicious that you might have acquired infection with coronavirus or another respiratory virus,” said Richard Harvey, vice president of the Australia and New Zealand Rhinologic Society.
Reports from South Korea, China and Italy have identified significant numbers of COVID-19 patients who have developed either partial (hyposmia) or total loss of smell (anosmia), said a joint statement from the presidents of the British Rhinological Society and ENT UK.
A statement from the American Academy of Otolaryngology — Head and Neck Surgery also identified anecdotal evidence of a diminished sense of taste (dysgeusia) in some people.
The problem is for many of these patients, loss of the sense of smell has been an isolated symptom, without the other typical symptoms that we are associating with COVID-19, said Perth ENT specialist Peter Friedland.
That means people who had no other symptoms, or were perhaps only in the very early stages of the disease, could have been going out in public and spreading the virus without realising they were infected.
But you can also temporarily lose your sense of smell if you have a very severe cold, or very bad allergies.
“So the question is how does one differentiate between having a cold that is so bad, and COVID-19? And really the answer is test people,” Professor Friedland said.
However, currently in Australia, you do not meet the criteria for COVID-19 testing if you have lost your sense of smell.
What to do if you suddenly lose your sense of smell
“Self-isolate and stay home,” Professor Friedland said.
Professor Harvey recommends trying to book in a telehealth consultation if you can.
This means you can continue to self-isolate and speak to either your GP, or a specialist, to discuss your anosmia and any other nasal symptoms that might alert them to other causes of smell loss.
“There are some early interventions one can do to help protect the degeneration of the smell centre, and then promote early recovery,” Professor Harvey said.
They’re relatively low risk and could be followed for a month or two even without being formally examined by a doctor in person.
If you develop other symptoms of COVID-19, you should contact your GP or the Government’s hotline (1800 020 080) to find out whether you are eligible for testing.
Why can you lose your sense of smell when you have COVID-19?
“Perhaps the most important real estate in the nasal cavity sits in the roof of the nasal cavity,” Professor Friedland said, “just between our eyes.”
That’s where the brain meets the roof of the nasal cavity, known as the olfactory bulb, and it sends very delicate little fibres through what’s known as the cribriform plate.
These olfactory fibres supply a tiny little area called the olfactory epithelium — it’s a couple of millimetres across — which is responsible for our sense of smell.
“That’s why people sniff or breathe in, when we want to smell because we want to get the smell up to that little area,” he said.
When we have a cold, the path to that area is obstructed because we’ve got inflammation in the nose so smell particles can’t get up there.
But this coronavirus is a tiny particle so it can reach that area, and it actually affects the lining and the receptors in the roof of the nose.
This area, together with other nasal tissue, is rich in ACE-2 receptors which the virus attacks.
“This is a mechanism which actually damages the lining of those olfactory cells,” Professor Friedland said.
How long will you lose your sense of smell?
While he doesn’t want to make people panic, Professor Friedland said if you lose your sense of smell it’s not clear whether this is a permanent or temporary situation. And losing your sense of smell can also mean losing the subtleties of taste.
Our olfactory centre also has some ability to regenerate, Professor Harvey said.
People who have had injuries to their olfactory systems can go through a program of olfactory retraining.
If you do lose your sense of smell you need to be careful as you could miss warning signs for things like leaking gas or fires.