A tell-tale and common symptom of COVID-19 infection is a loss of smell.
It's not a life-threatening symptom but can have a profound impact on a person’s life, especially if it's persistent. Anosmia can last for weeks or even many months.
With doctors under intense pressure because of the pandemic, a free online smell training programme called NoseWell has been developed which people can use themselves to try to regain their sense of smell.
NoseWell is a collaboration between the British Rhinological Society (BRS), ENT UK and the charity AbScent.
Medscape UK spoke to Professor Claire Hopkins, president of the BRS about anosmia and how smell training works.
When did loss of smell first come to light as a possible COVID-19 symptom?
Around mid-March I started to see a dramatic increase in people presenting to me with a sudden loss of smell. They had no other symptoms, no cough or fever but some had a mild flu-like illness, or a history of travel, but not to China or Italy. I spoke to colleagues in France, Italy, and the US and we had all seen this increase. In particular, colleagues working on the front line in Italy had lost their sense of smell without any other symptoms of COVID-19 infection.
Loss of smell with most viruses only affects maybe one percent of people, and it's typically associated with nasal congestion and running nose, so this was unusual. Very quickly we realised this was potentially a very important marker of COVID-19 infection.
Starting from mid-March onwards I started discussions with Public Health England and collected data. One of the first papers we published, in JAMA, looked at 200 patients diagnosed with COVID-19 of whom 60% reported having suddenly lost their sense of smell. Groups all around the world collected very similar data. It very quickly emerged that loss of smell is one of the most common symptoms of COVID-19 and also, most importantly, it's the best predictor.
There are many things to cause you to have a temperature, or cough, but outside of having a head injury there are very few things which cause a sudden loss of smell.
We have now shown that if you suddenly lose your sense of smell in the current times there's at least a 95% chance it's due to COVID. So, it's a good marker of infection and probably even more reliable than a COVID test, which can give false negatives.
When was loss of smell officially accepted as being a symptom of COVID-19?
The World Health Organisation recognised it as a symptom in April. Public Health England didn't accept it as a symptom until May 18. We were one of the last countries to recognise it officially, even though much of the research had come from the UK.
How many people with COVID-19 lose their sense of smell?
If you look at patients with COVID who self-report a loss of smell it's about two out of three. It's more commonly reported in people with a mild infection rather than those with a more severe infection. That may be to do with the fact they are too ill to notice as they are struggling to breathe or aren't eating or drinking. Older age groups tend to have more severe infections and also have a higher rate of losing their [sense of] smell from ageing, so they may not notice the difference. It does seem to be more common in women, but that may be because men are more likely to have a severe disease. When you formally test loss of smell it's more detectable, even if patients aren't aware of it. We have found, as I said, that as many as 95% of people with COVID have a reduction in smell but they might not all be aware of it.
When do COVID-19 patients tend to get their sense of smell back?
It's split into two groups. About 50% fully regain their smell and taste within 2 to 3 weeks. I say smell AND taste because patients often report having lost their taste. They may be able to differentiate between sweet, salty, and sour, but have lost all the super-added flavour you get from smelling our food as we eat. Some may also lose their true sense of taste as well as smell, but it's usually short-lived and recovers before smell.
In about half of those affected it seems the injury to the supporting epithelial cells in the nasal passage is relatively mild and they can recover before any damage to the olfactory nerves themselves is done.
Forty percent will report they have largely recovered completely by 8 weeks, 10% will report at 8 weeks that they haven't recovered. Six months down the line only about two percent still haven't recovered their sense of smell at all.
Some patients experience parosmia, which is when smells take on an unpleasant odour. We think smell training might be able to help people with parosmia to get a better functioning point more quickly.
Although not a threat to life, can the loss of smell have a debilitating effect on people's lives?
Yes absolutely. That's really underestimated and is one of the struggles these patients face. It has huge effects on emotional wellbeing, memory, and it is associated with quite high levels of anxiety and depression. It's very difficult for friends and family, and sometimes health care workers, to understand that and be supportive of it. A lot of patients feel they have been dismissed by their doctors, some have been told 'at least you didn't die from COVID' or 'it could have been worse, you could have gone blind'. Many others don't understand the impact, especially if after 6 to 9 months there's been no improvement. People lose some of their sense of self-identity, they worry about body odour, they worry about fires, and they can lose the enjoyable social aspects of the modern world such as getting pleasure from eating with family and friends.
Should health professionals point patients to the NoseWell smell training?
Early on we recognised that huge numbers of people were affected and were finding it difficult to access medical help as the system was overloaded. The doctors that they went to see weren’t familiar with smell loss and how to treat it. There is good evidence for smell training. It was originally developed by Thomas Hummel in Germany in 2009. Smell training accelerates recovery and improves the ability to detect smells and differentiate between them. We think that's because as the olfactory nerves are regenerating, they have to make both the right connections in the nose and in the brain. As you encourage those connections it improves the ability to detect.
To try smell training you can use anything with a strong odour that you have around the house, but essential oils are often used. You really think about what it smells like. So, when you are sniffing the lemon fragrance you are really thinking about how a lemon used to smell to you.
It's about encouraging focus on the lemon smell and the central processing that goes with this. Most GPs and ENT surgeons may not be familiar with this and a lot of patients were going to the internet for information. You can do smell training at home and don’t need the support of medical personnel. With NoseWell, we wanted to be sure that information was widely available for members of the public to access the resources themselves.
Does it matter what the scents are and how long does it take to work?
Rose, lemon, eucalyptus, and clove are recommended as they cover different types of odours and are likely to stimulate a different pattern of odour receptors. We encourage people to start with those and continue for the first 12 weeks. There are instructions on the NoseWell site as to how patients can make up their own kits, or AbScent is selling pre-packaged kits with any proceeds going back to the charity. Similar information is also available from Fifth Sense.
We know from randomised trials that patients who do smell training have better outcomes than those who don’t. It’s little and often and doesn't take long. It's not something that gives instant results, but more of a gradual improvement.