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The pandemic has taught us that we ignore the “Cinderella sense” at our peril. I’m stalked by a smell. It’s lurking in my kitchen, in my bathroom, on my breath. It settles on the surface of my coffee and, sometimes, my skin. I can smell it in my perfume and all the food I eat. Most days I think it’s onion, but it’s also close to garlic, or gas, or garlic cooked on gas.

It is not, curiously, a scent I had smelled before October, and yet it’s there all the time, right under my nose. I caught Covid that month, and the smell has plagued me since.

Around 65 per cent of people who test positive for coronavirus lose their sense of taste and smell; roughly 8 per cent say these symptoms persist at least five weeks after infection. This means more than 300,000 people in the UK alone have suffered, or are still suffering, from “long haul” Covid smell disorders.

For those people, Covid-19 has changed not only their way of life but their way of being in the world. This is not an overstatement. Our ability to smell is fundamental to our sense of self: it is a consciousness modulator, a danger detector, a decision-making trigger, a relationship maker-and-breaker. It is the body’s most trusted gatekeeper. And yet for so long we’ve dismissed smell – what its researchers call the “Cinderella sense” – as nothing more than a nice-to-have.

In 2018 YouGov played a classic after-dinner game with around 20,000 Americans, asking which of the five senses they thought they would miss the most. Seventy per cent said their sight, and 7 per cent their hearing. In last place, with 2 per cent, was smell. In a separate survey of 7,000 16- to 22-year-olds, more than half said they would rather disable their sense of smell than their computer or smartphone. What is it about smell that fails to make an impression on us? Or, rather, why do we fail to make a meaningful impression of it?

Smell is partly a casualty of language: when we talk about “taste”, we don’t really mean taste alone, since our tongues can only tell us if something is sweet, salty, sour, bitter or umami. Rather, it is our noses, discriminating between many thousands of odorants, that give food its distinct flavour. And although we have the vocabulary to describe scents and the capacity to commit them to memory (perfumers learn up to 2,000 odorants), most of us are not in the practice of identifying, for example, whether wine is more “black fruit” or “red fruit”, “blackberry” or “blueberry”; most of us are happy to call it “fruity” and move on.

“People used to think we only smell when we sniff, but that’s not true… We smell because we breathe.”

Most of all, unlike objects in our visual field, smell exists in a curious dimension, somewhere between our conscious and unconscious perception. Smell seems to announce itself to us only fleetingly as we interact with our physical environment, so that often we forget it’s there at all. “You don’t tend to notice things that are always on,” said Barry Smith, a professor of philosophy at the School of Advanced Study, University of London, and the UK lead for the Global Consortium of Chemosensory Research.

We can shut our eyes, he said, but smell is a constant “background to consciousness”, modulating our awareness and emotions in ways we cannot always point to. If we step outside and the spring air feels “fresh”, this is partly thanks to smell, but perhaps we might not recognise it as “smell” in any conscious way. “People used to think we only smell when we sniff, but that’s not true,” Smith said, referencing the 20th-century American psychologist James J Gibson: “We smell because we breathe.”

The pandemic has taught us that we ignore smell at our peril. During the first wave, even as evidence came from South Korea, China and Italy suggesting a link between Covid-19 infection and anosmia or hyposmia (complete or partial absence of smell), it did not appear on official symptoms lists for months. The UK finally listed it in mid-May, eight whole weeks after Claire Hopkins, the head of the British Rhinological Society, argued people suffering sudden smell loss should be asked to self-isolate. She later told the New York Times she believed officials were slow to act, in part, because smell loss had been obscured by the seriousness of other symptoms, but also because smell has never itself been regarded as “serious”.

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Covid-related smell and taste loss is sudden and distinct, quite unlike the congestion you might experience if you catch a cold. Research suggests this is because the virus works not by blocking the airways but by invading support cells in the nasal cavity, causing inflammation, which means the olfactory neurons no longer have the support they need to send effective smell signals to the brain. This could explain why some people recover their sense of smell quickly, within the time it takes for the surrounding cells to heal, while for others, the inflammation is so acute that the neurons themselves are damaged and have to regenerate.

Many Covid patients find that when their smell returns it comes back warped. Some detect “phantom” odours that aren’t really there (“phantosmia”), while others report distorted smell (“parosmia”). Suddenly, ordinary things – food, soap, perfume – smell unusual and often disgusting. Many say their “parosmia” smell resembles burning, petrol, fish or rotten flesh. It is almost always overwhelming.

The prevailing wisdom is parosmia is a good thing – a sign of the neurons regenerating but failing to make their connection, like leads in the wrong port. But, Smith tells me, it’s not a simple “miswiring”. There appear to be certain volatile molecules, such as those found in coffee and roasted meat – which in high concentration would be quite toxic – that set it off, perhaps triggering a kind of warning alarm.

“It’s a bit like tinnitus in the ears,” Smith suggests, in that the brain is struggling to modulate the signals it receives; my nose is whining, always at the same high pitch.

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People with smell disorders often rapidly lose or gain weight (bingeing on salty, sweet or fatty foods is common, as those without taste go in search of a “hit” they can’t find). But smell loss does not only disrupt our relationship with food.

Chrissi Kelly, the founder of the UK charity AbScent, which supports people who have lost their sense of smell, told me that smell disorders can seep into all aspects of our emotional and private lives. Kelly has heard from parosmics who say they can no longer bear to kiss their partner, because the smell of their breath or personal odour repulses them. One mother, who caught Covid at hospital while there to give birth, told of her distress at not being able to smell her own baby.

Kelly lost her smell after a severe sinus infection in 2012 and became depressed before it started to return after two years. “It was a very destabilising experience for me,” she said. “When you get no feedback from your own personal smell or your immediate environment, it’s very odd. It takes away a dimension.” Studies show there’s a bidirectional link between reduced smell and clinical depression.

It’s physiotherapy for the nose

An additional pain of smell loss, Kelly notes, is that it’s hard to communicate how it feels. Many anosmics, trying to capture their feelings of isolation, speak of being trapped behind a sheet of glass, or in a helmet or a bubble.

“In almost nine years I’ve never found an adequate analogy,” Kelly said. “I’ve been trying to find one that speaks to the ‘elementalness’ of smell; trying to find an aspect of life on Earth that is so integral to what it means to live on this planet that you’ve never even really considered it.”

This relationship, between olfaction and the nature of our existence, fascinates the cognitive scientist Ann-Sophie Barwich. She writes in her recent book Smellosophy that “odours have always presented an ontological problem”, offering up puzzles about human exeperience and perception: what does it mean to perceive smell? How do we know that what we perceive is real? I tell Barwich that I no longer feel immersed, that I’m somehow detached, not only from my immediate environment – the smell of the shower, the street after it’s been raining – but also from others. A meal with my flatmate is no longer really “shared”; on walks with friends, I notice how often smell comes up – “that bakery smells amazing”, “that man’s aftershave is strong” – and it’s as if we’re moving in different worlds.

“You’ve basically got two effects with smell loss,” Barwich said. “You’ve got your own landscape of experience that’s changed; and there’s also the lack of a common social space.” She says it’s like a “sensory version of social media” in that, if you’re not on it, there are so many references, so many points of contact, that are completely inaccessible to you. “It’s as if you’re not on the medium.”

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Each morning, I get up and sniff four scents – rose, eucalyptus, clove, lemon – each trapped in tiny amber jars. Very little is known about how smell conditions should be managed, still less about how they should be treated, but smell training – actively smelling these four scents every day – is thought to aid recovery. It’s physiotherapy for the nose. Kelly tells me it helps to try and capture “smell memories”, which are tied to an emotion, and to imagine them when I’m training. So I sniff, and I conjure up the rose bush in my dead granny’s garden, the lemon verbena of childhood holidays in Spain. It’s some comfort; but it’s not a cure.

Covid could represent a turning point in our understanding of smell. Across the world, there are potentially hundreds of thousands of people who will never fully recover their smell, many of whom may require psychological support. These people, Smith said, with all their data and observations, may also contribute to a new period of “citizen science” in the study of olfaction, guiding the scientific questioning and directing researchers’ attention.

Barwich hopes the pandemic might also serve as a meaningful lesson in empathy; that for those suffering chronic smell loss, there will at last be a certain translatability of experience, now that we all live lives in which something is missing. Under lockdown, sensory deprivation is almost universal: most of us live and work with no new voices in the room, no brushes with strangers or hugs with friends. Sights and sounds are limited to our four walls and our walks. “And a lot of people are feeling this, that something is lacking,” she said, “but we don’t have a good word for the absence.” We’re all, one way or another, trying to find sense in things.

Source: Searching for sense: what we lose when smell deserts us

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Random sensory quotes

Instinct is the nose of the mind.

— Delphine de Girardin