Making sense of smell
loss after brain injury


NR Times, 7th January, 2021

"Like living behind a pane of glass"

Up to three and a half million people in the UK could be experiencing smell loss, with head injury among the top four causes. But often it goes untreated for years, despite having a profound impact on a person’s quality of life. Sarah Sinclair reports on a webinar on the topic. 

Duncan Boak can’t tell when the milk has gone off. Nor can he remember the smell of fresh basil, even though he chops it every time he cooks a tomato sauce. 

After suffering a head injury in 2005, Duncan lost his sense of smell. “I was in hospital for a week after the accident, eating very little. It was when I came out of the hospital and had the first meal since the accident at my parent’s house when I realised I couldn’t smell anything,” he says.

“I went to see my doctor and was told nothing can be done, he said to give it time, that it might come back on its own accord and if it doesn’t ‘you will just have to live with it’.”

At the time Duncan felt that he had gotten off lightly, but in the months after the accident he began to experience depression. 

Without his sense of smell he lost his appetite and, as a result, a lot of weight. “I’m a pretty slim guy anyway, but I was a bag of bones for a while,” he says.

“The thing with loss of smell is that there is a lasting, ongoing loss of quality of life. We’re not just talking about the eating experience, it’s the removal of a really important emotional connection to the world around us and to people in it.

“There is an ongoing feeling of disconnection, of being removed from the world. It can be a bit like watching life from behind a pane of glass.”

In 2012, Duncan founded Fifth Sense, the charity for people with smell and taste disorders.

A survey of its members published in 2014 as the Impact of Olfactory Disorders in the UK, found 92 per cent of respondents had found their enjoyment of food and drink had been reduced since losing their sense of smell.

In addition, 54 per cent had had relationship difficulties and 43 per cent experienced depression.

“It has a huge range of impacts, not only on the eating experience, but much more widely,” continues Duncan.

“You lose memories of smells and tastes, but some of the other dangers and difficulties include loss of confidence in your own abilities and there's the safety aspect - the fact you can’t smell gas or burning, or if food has gone off.

“If I’m worried about the milk I have to rely on my flatmate to smell it for me, but the safety aspects can be a greater concern for people who live alone." 

Making sense of it 

Research has shown that at least one per cent of people in the UK lack the ability to smell, with potentially five per cent (up to 3.5 million) reporting an impaired ability to smell.

But some studies suggest that experiences of smell loss could affect up to a quarter of the population.

There are various ways in which smell disorders can present: anosmia, where a person has no sense of smell; hyposmia, a reduced sense of smell; phantosmia, smelling smells that aren’t there and parosmia, having a distorted sense of smell, sometimes described as a smell of burning rubber or a pungent chemical smell or raw sewage.

According to Professor Carl Philpott, director of research and medical affairs for Fifth Sense, and Professor of rhinology and olfactology at the University of East Anglia, smell loss is as prevalent as sight loss and hearing loss in the UK, but often goes unreported.

“If it affects about five per cent of the population, that is more than sight loss in the UK [three per cent], and also profound hearing loss [one per cent], yet as things stand we don’t have a Royal National Institute to consider and account for patients with these disorders,” he says.

Head injury is among the top four causes of smell loss, along with chronic sinusitis and respiratory tract infections such as common colds, the influenza virus and, more recently of course, the coronavirus. 

But it can also be caused by comorbidities or long-term conditions such as Parkinson’s Disease or cancer.

“For those of us that run specialist clinics, head injury is a much more common presentation and post-traumatic olfactory loss (PTOL) is one of the most common reasons for people to present at my smell and taste clinic,” Prof. Philpott continues.

“It is thought that about one in three motor vehicle accidents involve the head neck region, and therefore it’s not surprising that loss of smell may accompany that.

“The other key thing is whether there’s any associated facial injuries, such as after an assault that results in a blockage to the nose.

“It can also be caused by a bruising of the brain - what we call a contra-coup injury or due to shearing of the fine olfactory nerve fibres as they cross the skull base from the nose into the brain.

“Occasionally, it could be that an individual patient already has a pre-existing problem with their nose and sinuses and the head injury exacerbates that underlying disorder.

“In cases where the TBI is thought to be a grade one, then the chance of olfactory dysfunction is around 18 per cent, but in cases where the injury is grades two and three, this goes up to 57 per cent.

“We think in head injury clinics around 10 percent of patients are reporting smell loss and probably not really getting much further action from there,” he adds, but believes this is an underestimate, with several reasons why patients might not speak up about smell loss.

For those who have suffered an accident, they may spend a long period of time in intensive care and are therefore not in a position to be aware, or may be dealing with much more severe injuries, and so a loss of smell is not a priority. 

Those who are conscious but in hospital may assume that the lack of ability to smell is down to the poor quality of hospital food. However, early recognition is key for treatment, with any recovery most likely to occur within two years after the head injury.

“Smell training is really a very simple but key thing that patients can do,” says Prof. Philpott. 

“Those who benefit tend to be younger, have a shorter duration of the disorder and less severe trauma, so getting people to see a specialist sooner rather than later is always beneficial.” 

He continues: “We can see partial recovery in about one in three people after head injury related smell loss, but complete recovery probably only occurs in about 10 to 15 per cent of cases. 

“The greatest chance of improvement is in that first period between up to 12 months. There is a potential for improvement after that period, but it becomes much lower.”

Last year, Fifth Sense developed SmellAbility – a toolkit to enable people to build their own smell training resources and provide physiotherapy for the nose.

SmellAbility provides information about the science behind smell training, tests to establish baseline ability, record sheets to measure how this changes over time and a diary log to record training, all of which can be downloaded or printed for use.

“It is important that people create their own smell training resources whether it is following the science and using essential oils, or using everyday items they have at home.

"We encourage people to choose a range of smells that they are familiar with so that they will recognise any changes or improvements,” says Nina Bleasdale, director of development and operations.

She goes on “we encourage people to use their other senses to support them. Take a real orange, grate the skin (which actually releases the natural oil used in creating essential oil), use your sight to enjoy how the orange looks, touch it to stimulate its full appeal and use your memory of what an orange smelled like to you – all of which can help to get the most from smell training”. 

"It’s only smell"

Fifth Sense has lots of resources on its website to provide support and guidance for people experiencing smell and taste disorders, as well as running regional support hubs around the country in partnership with specialist smell and taste and rhinology clinics. 

Duncan says: “We’ve done a lot of work over the years to bring the people we represent and their families together, alongside clinicians and scientists, and give them the opportunity to share their stories and challenges.

“This can be really beneficial for people, and encourages wider understanding."

More recently Fifth Sense has been running successful ‘Let’s Talk Smell and Taste’ virtual conversations, supported by funding from the National Lottery Community Fund and the British Rhinological Society.

The charity also does a huge amount of work to raise awareness, and works to promote, support and facilitate research in an area where much more is needed.

Fifth Sense is working with others to change this. It is collaborating with the James Lind Alliance, part of the National Institute of Health Research, to undertake a Smell and Taste Disorders Priority Setting Partnership, which will give patients, their families and clinicians the opportunity to set out their priorities for future research.

“There is nothing more powerful than hearing a patient’s voice explain what might be important to them,” says Nina, who has experienced phantosmia on and off throughout her life.

“There’s relatively little clinical research being undertaken and a lack of awareness of 

the deep and profound role that smell plays in our lives. “Quite often people are told by their GP that there’s nothing that can be done and ‘it’s only smell, it could be worse, at least you can still walk’.” 

Ironically, Nina believes the fact that loss of smell has become a common symptom of the coronavirus has helped improve awareness of its importance among the public and medical profession. 

“I’d like to think as a result of the pandemic awareness in the medical profession certainly has improved,” she says. “As people’s smell isn’t returning as quickly as they thought it would following Covid, a lot of people are saying they didn’t realise how important smell was until they no longer had it. 

“A lot of the research currently being conducted is around smell loss associated with Covid, which ironically, is a good thing for people with smell and taste disorders. Awareness is being raised as a result of it becoming a much more common health condition.”

Nina adds: “For many it could be an invisible disability, you can’t tell it would affect a person’s ability to do things, but a chef may feel they can no longer cook to high standards because they cannot smell and taste their food properly, and a gas engineer may be at risk if they weren’t able to smell gas. It certainly prevents people from doing certain jobs.” 

Food for thought 

A loss of smell can have a much greater impact on a person’s physical and mental health, according to Sian Riley , a registered dietitian and director of Red Pepper Nutrition, specialising in nutrition following a traumatic injury. 

“Before foods even touch your mouth, you will smell it. All those molecules from the food form a communication signal to the olfactory bulb, which continues the same signal on to the amygdala and the hippocampus which are areas in our brain involved in emotion, memory and learning. 

“That smell is communicating an emotional message to us and from there the brain sends signals which regulate our appetite.”

Sian continues: “Quite often, with a brain injury, many of those olfactory receptors are lost, therefore you’re not getting this communication before the food has entered the mouth. You’re not building a picture of the food. 

“Food is complex. The psychological and emotional side of food is really important, as is the social side.”

This was true in Duncan’s case. He no longer found pleasure in food and as a result not only felt his appetite slipping away, but his connection to the world too.

“One of the hardest things is this feeling of detachment from the world around us and from life’s pleasurable experiences,” he says.

“So many of our social interactions take place around a meal, if you take away the pleasure of eating and drinking then sometimes people don’t want to go out for meals anymore, they don’t want to have food with friends and family. It can be very difficult.

“It really impacted on my ability to form close relationships with girlfriends for a long time.”

This is something Sian sees a lot with clients who are experiencing smell loss. But as well as their mental health, it has huge risks for their physical health too.

“Smell disorders will decrease the enjoyment of food and decrease our appetite and this will have a knock-on effect on the nutrition we’re getting,” says Sian.

But not just in terms of weight-loss and malnutrition. The need to feel satisfied by a meal, may lead people to add too much salt or sugar to compensate for the loss of smell or taste.

“After a meal we need to feel satisfied and if we’re not feeling satisfied by the food, then we need to find a way of using our other senses to make it more satisfying,” she explains. “We might add more salt, so that we can taste it, more sugar, or more fat, because that feels good in our mouth, all this is increasing the risk of obesity and heart disease.”

Instead, Sian recommends that her clients practice ‘mindful eating’ and stimulate their other senses when it comes to food, focusing on the colours, textures, appearances and temperatures in their meal.

Duncan has become finely tuned at detecting subtle differences in whether food is sweet, sour or salty and uses mindfulness techniques to be more aware and appreciative of what he enjoys.

“I might not be able to get the flavour of basil, but I still use it, because it’s about creating visual contrast, making the food more stimulating given that I don’t have the smell of it to stimulate my appetite,” he says.

“Experimentation is really important, trying things that you’ve never tried before, even things that you once disliked, and paying attention to the elements that you’re still able to detect.”

Everyone at Fifth Sense would agree that recognising and talking about smell disorders and sharing these experiences with friends and family is vital to avoid the sense of isolation and ‘living behind a pane of glass’ that Duncan felt.

“Talking about it is really important,” he adds. “This is something that people find very hard to do, but I would encourage anyone affected by a smell disorder to talk about how you feel and the impact your condition has on your life.

“When it comes to food, talk about the elements of a meal that you are still able to appreciate and enjoy with your partner, family and friends to help them understand, and to help them create meals that work for you.” 

Duncan Boak, Fifth Sense

Duncan Boak, Fifth Sense

Sian Riley, Red Pepper Nutrition

Sian Riley, Red Pepper Nutrition

Smell and taste
disorders in numbers

57% of people affected feel alone and isolated

92% say they appreciation of food and drink is reduced

43% have suffered depression as a result

54% have experienced relationship problems

85% are afraid of being exposed to dangers such as gas


Source: Fifth Sense