COVID-19  A loss or change to your sense of smell or taste could be coronavirus

Case reports suggest that anywhere between 34 and 98 percent of hospitalized patients with COVID-19 will experience anosmia. Data show an average loss of close to 80 percent of normal smell function, 69 percent of normal taste function, and 39 percent of normal chemesthetic function from COVID-19 infection. One study found that COVID-19 patients are 27 times more likely than others to lose their sense of smell, making anosmia a better predictor of the illness than fever. However, recovery can be rapid; nine in 10 patients can expect substantial improvement in their sense of smell within four weeks (BMJ 2020)

If you are concerned then GOTO NHS covid-19/symptoms/

How is the sense of smell lost?

The findings suggest that infection of nonneuronal cell types may be responsible for anosmia in COVID-19 patients. SARS-CoV-2, like the earlier known SARS-CoV, uses the angiotensin-converting enzyme 2 (ACE2) receptor to gain entry to cells via binding with spike protein. Olfactory receptor neurons do not express ACE2. SARS-CoV-2 additionally appears to need TMPRSS2, a protease, to help prime the spike protein in the process of gaining entry to cells and a few other proteins. This means that cells must express all of these proteins for the virus to be able to infiltrate them and hijack their machinery to replicate. ACE2 and TMPRSS2 are expressed in many types of cells, and quite abundantly in the nose, throat, and upper bronchial airways. In the nose, expression is seen in both the respiratory epithelium (RE) and the olfactory sensory epithelium (OSE) but in much higher levels in the OSE. In the OSE, the proteins are expressed in the sustentacular (supporting) and olfactory stem cells as well as in the Bowman’s (mucus) glands and microvillar cells in lower levels. All of these cells help maintain the health of the sensory neurons and the mucus layer so that odors can properly activate the neurons. So far, it appears that olfactory sensory neurons themselves do not have the right expression patterns to bind SARS-CoV-2, which means that the virus may not directly invade these neurons that synapse directly in cortex in the olfactory bulbs (ref: Scientific American).

Loss of taste

Taste receptor cells, which detect chemicals in the saliva and send signals to the brain, do not contain ACE2, so they probably do not get infected by SARS-CoV-2. But other support cells in the tongue carry the receptor, perhaps providing some indication of why taste goes away. (Although taste can seem to disappear with anosmia because odors are such a key component of flavor, many people with COVID truly develop ageusia and cannot detect even sweet or salty taste.)

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Another function of the sense of smell - navigation

18 October 2018. Interesting research from Canada on the correlation between the sense of smell and ability to navigate. This was based on the idea that the sense of smell evolved to aid navigation. The research findings which show that olfaction and spatial memory are connected and this is supported by a shared use of the same brain areas (hippocampus and medial orbitofrontal cortex). The suggestion is that the olfactory and hippocampal systems evolved together.

Dogs sniff out malaria

BBC World Service (29 October 2018)  Researchers in Britain and The Gambia say they have the first evidence that dogs can sniff out malaria, a skill that they say could lead to much quicker diagnosis of the killer disease. The work was done with the charity Medical Detection Dogs.
The dogs were trained to smell the presence of the malaria parasite in infected children by sniffing their clothes.  The researchers say that in addition to screening local communities, sniffer dogs may one day be used at airports to detect malaria carriers to help stop cross-border infection.

Hair Follicles Can 'Smell' Sandalwood

Hair follicles contain an olfactory receptor, OR2AT4, which binds to synthetic sandalwood - sandalore.
Adding the sandalore increases production of a growth factor (IGF-1) by hair follicle cells and this decreases apoptosis (cell death) and prolongs human hair growth. The work was done on explanted human skin taken during face lift surgery which was then cut up into small pieces. The work is published in Nature Communications, lead author Ralf Paus. It is suggested that this might lead to a cure for baldness.

Cautionary note: Some years ago (2003) research was published by Mark Spehr and others in Science showing that sperm smell their way to the egg stimulated by the compound bourgeonal secreted by the egg. This was promoted as a possible treatment for infertility. Sperm were found to contain the olfactory receptor hOR17-4 that binds boureonal which is the smell of Lily of the Valley.
A detailed explanation for the Lily of the Valley phenomenon remained illusive as neither Bourgeonal nor other scents could be identified in the female sex organ. In a recent publication in EMBO J (2012) scientists from Bonn have now discovered that sperm do not function like olfactory cells - a finding that casts doubt on the assumption that scents play a role in fertilisation.  They found that the Lily of the Valley scent only works at unrealistic concentrations. Therefore, scents only work if overdosed. The “Lily of the Valley phenomenon” is a laboratory artefact: sperm do not have an olfactory signalling pathway.

Olfaction wins an IgNobel prize!


Paul Becher, Sebastien Lebreton, Erika Wallin, Erik Hedenstrom, Felipe Borrero-Echeverry, Marie Bengtsson, Volker Jorger, and Peter Witzgall, for demonstrating that wine experts can reliably identify, by smell, the presence of a single fly in a glass of wine.

REFERENCE: "The Scent of the Fly," Paul G. Becher, Sebastien Lebreton, Erika A. Wallin, Erik Hedenstrom, Felipe Borrero-Echeverry, Marie Bengtsson, Volker Jorger, and Peter Witzgall, bioRxiv, no. 20637, 2017.

Smell and light mood boost - measured

Fluctuating bright light (10,000 lux) and synchronous smell stimulation. You can measure an increase in mood-energy in response to this innovative therapy. This could be used for treating those with mood disturbances (e.g. anxiety, depression). More information on the technology is given in the Therapeutic Uses of Smell pages.
Fluctuating light and smell stimuli were given to 18 subjects for 15 minutes using the Kodobio. The subjects answered a questionnaire before and after the session based on the Circumplex Model of Posner et al., 2005. The results shown in the graph are the averaged responses (mean +/- standard error, n=18) for "mood" and "energy". It works to improve mood and sense of energy!

Stories on the sense of smell - National Public Radio (US)

Sound features on the sense of smell from US radio (13th Sept 2018), e.g. "Learn To Sniff Like A Dog And Experience The World In A New Way"

The Subjectivity of Scent

Interesting article on smell, from Fleur Fruzza in Women's Health August 2018.  "Been wedded to the same floral eau de toilette for more than a decade? Or do you hold fast to fragrance recommendations from a beauty-mad pal? Well, don't." Smell preference, smell affect, smell memory etc., with help from Prof Tim Jacob.

The Smell Podcast

Interesting podcasts on smell, from Katie Price. "The Smell Podcast, where we explore all things smell and taste. If you have a smell/taste disorder or are supporting a family member who does, this podcast is for you! We'll explore listener stories and current research on smell and taste!" It's on Spotify too - Smell Podcast.
(13th Sept 2018).

Gene therapy restores sense of smell (in mice)

Scientists have restored the sense of smell in mice through gene therapy for the first time — a hopeful sign for people who can’t smell anything from birth or lose it due to disease. The new findings come from a team at Michigan University Medical School and their colleagues at several other institutions. The researchers caution that it will take time for their work to affect human treatment, and that it will be most important for people who have lost their sense of smell due to a genetic disorder, rather than those who lose it due to aging, head trauma, or chronic sinus problems. But their work paves the way for a better understanding of anosmia at the cellular level (1st August 2018).

The smell of cities in the summer 

Does your city smell in summer? Why is this? Odor experts agree New York City is the most infamous for its summer stench, but other major cities like Philadelphia and San Francisco suffer from the same problem.  Does Venice smell - people say no . What is your experience? After all this time spent in your home city, can you actually describe what it smells like? Above all, what is its defining aroma?  Dr Victoria Henshaw, author of the Smell and the City blog, can give you some ideas as to how to appreciate your city's smells.

Thailand cave rescue: Children found ‘by smell’

John Volanthen, from Bristol, was one of a number of foreign expert divers drafted in for the rescue of 12 boys and their football coach who had been trapped in a Thai cave for nine days. Mr Volanthen, a member of the South and Mid Wales Cave Rescue Team, said they knew they had found them due to the smell in the cave. "Our procedure in this situation is we're swimming along an underwater passage, wherever there is airspace we surface, we shout and also we smell. In this case, we smelled the children before we saw or heard them.". BBC 13th July 2018

12th July 2018 - Swansea is starting to smell

An investigation has been launched. If you've been out and about enjoying the warm weather in Swansea recently you probably aren't the only person to have noticed an unpleasant smell.
For some residents across the city, evening walks along the promenade or trips down to Mumbles are being tainted by a faint odour filling the air of drains. A spokeswoman for the water services company said: "We are aware of reports of an odour affecting the city centre and Mumbles area of Swansea and are investigating if there is any link to our wastewater network".. I is now decades since Surfers Against Sewage was founded largely in response to untreated sewage on the South Wales coast?  More...

A new type of deodorant? Experts believe they have found a better way to tackle body odour (BO). The key, they say, is understanding how skin bacteria create the smell from virtually odourless armpit sweat.

AI is developing a sense of smell: to detect disease on human breath (The Conversation 8.06.2018). However there is some scepticism about how useful AI is/will be in detecting and categorising smells generally (Robert F. Service for Science 19 Feb 2017). You have to tell the computer/algorithm how it is supposed to classify aroma and if we humans aren't really sure then the computer just amplifies our ignorance.

The smell of rain "Petrichor".

  Old news but always interesting  [The Conversation  31.04.2015]  The term was coined in 1964 by two Australian CSIRO researchers, Isabel Joy Bear and Richard G. Thomas, for an article in the journal Nature. In the article, the authors describe how the smell derives from an oil exuded by certain plants during dry periods, whereupon it is absorbed by clay-based soils and rocks. During rain, the oil is released into the air along with another compound, geosmin, a metabolic by-product of certain actinobacteria, which is emitted by wet soil, producing the distinctive scent; ozone may also be present if there is lightning. In a follow-up paper, Bear and Thomas (1965) showed that the oil retards seed germination and early plant growth (thanks Wikipedia - yes, I donate regularly).

Uranus smells of rotten eggs

The planet’s cloud tops are partly made up of hydrogen sulphide, the same chemical that gives rotten eggs on Earth their disgusting odour (Independent  24.04.2018 - read more.

Using smell to alter crowd behaviour in Holland

Some tests were carried out using the smell of oranges of people who were arrested and it had a calming effect. Now they want to try it on large crowds in trouble spots. Probably unethical - read more; (8 Jan 2018).

Why big brand perfumes may be losing their allure

Big perfume companies such as Estee Lauder, L'Oreal and Coty have been having a tough time. Might the perfumed wind of change be in the air "Everything smells the same - people are getting bored of the big brands and want something different," says Nick Steward, the London-based founder of a new fragrance brand, Gallivant. Nick thinks that people now want something that the giants can't or won't offer. His range of unisex perfumes (in small 30ml bottles) are inspired by and named after cities such as Tel Aviv and London. Mr Steward says the smaller size makes them more affordable. The perfumes have been well received at the launch earlier this year, but he admits: "It's a really tough business to make money in."
My own personal ( opinion is that the perfume industry is creatively bankrupt and people are looking to "niche" perfumers to supply something interesting but there really is nothing genuinely new. The banning or restriction of certain key perfume ingredients by the industry regulatory IFRA has made the business of making perfumes really tricky. For instance, Channel No. 5 has had to be reformulated because the key ingredient Oakmoss is now restricted. I believe that the industry needs to do some homework and by that I mean some real science to find out what smell actually does. They have been incredibly reluctant to do this because they make money by just putting (cheap) smells in fancy bottles and wrapping them up nicely. So where is the motivation for change? What could perfume do? Well, here is one thing: it could help you find your perfect partner and it could then help keep them interested in you. The science behind this is known but the industry are not interested. Yet!   04/10/2017  BBC News story

NEW! A new device to tell you if you smell - the KunKun Body. 

The Guardian (13th July 2017) reports on this new development from Minolta.
"Kunkun Body connects to your smartphone via Bluetooth. It is a pocket-sized device that lets you test your stinkiness in four different locations. It was developed by Japanese camera manufacturer Konica Minolta. The device can be used to scan your feet, behind the ear, near the head and of course your armpits. It tests for three different smells and checks for readings of sweat, middle-fat odors and a third category called kareishu, which apparently translates to “old age smell.” It then displays the results using a smartphone app."


Humans sense of smell claimed to be as good as dogs

Science article by Prof McGann from Rutgers  tries to make out that human sense of smell is on a par with other mammals, e.g. dogs (read article). No! I completely disagree. A bloodhound can tell the direction of travel of a human trail by sniffing 5 steps. Can you? What's your opinion? Leave a comment. (11 May 2017)

More on the Vibrational Theory of Smell

New article in PNAS tries to refute the "vibrational theory" of smell - and fails.
Eric Block and others have performed experiments to test the claim that deuterated compounds smell different from their nondeuterated analogues because, although they have the same shape, their vibrational signature is different. The paper in PNAS is focussed on refuting Luca Turin's 2013 PLoS paper "Molecular Vibration-Sensing Component in Human Olfaction". This new article describes the use of a heterologous gene expression system in which one receptor - OR5AN1 - is exposed to a series of deuterated musks and apparently does not distinguish between deuterated and nondeuterated versions. Luca Turin points out in Phys Org
that this does not explain how or why deuterated musks smell different from their nondeuterated counterparts and points out that this cell based expression system is a long way from the human nose.

Scents to make you smell younger in the Daily Mail (13 Apr 2015). Probably not

Olfactory ensheathing cells used to help paralysed man walk again
A man who suffered a spinal cord injury following a knife attack has been enabled to walk again. Cells from his own olfactory bulb were taken and grown in culture. They were then microinjected into regions around the spinal cord injury. Two years after the treatment he is able to walk again using a frame.

Sense of smell a predictor of death
 In a study of over 3000 people aged 57-85, 39% of those with anosmia (loss of sense of smell) were dead within 5 years compared to 10% with a normal sense of smell. So, losing your sense of smell is linked in some, unknown way to overall health and longevity. The conclusion is that smell function is linked to health and wellbeing and olfactory function is a marker for mortality.

Men are from bacon, women are from lemons
Did you know men and women are different, because they are. They are so different that they even like different things. Men like meat, visual stuff. Women like lemons, feelings. It's a wonder it ever works, because meat and pictures and lemons and feelings go together like a tornado in a teacup without any good smells in it. 
21st August 2014

Oh, and by the way there really is a bacon scented perfume for men

Losing your sense of smell can make you fat and destroy your libido - Daily Mail article

The sweet smell of success. Does success really smell sweet? A panel of 200 of Britons with 'sophisticated noses' sorted through over 100 individual smells from candy floss to urine to identify the aroma. They found the smells of leather, cedarwood and pencil are not associated with successful business people Patchouli, which is popular in joss sticks, is the scent most associated with successful men and women.

Potential future cure for anosmia - work in mice has shown that stem cells in the nose ca nn grow and develop into smell receptor cells. They can be made to do this by removing a gene that codes for a "brake" to growth in these cells.

Cancer detected by smell - Dogs can be trained to detect cancer (first shown by a UK lab - see below - Dogs sniff cancer) but now a machine is being developed to "sniff" cancer. Metabolomx, a small company in Mountain View, California plans to bring a cancer-sniffing device to market. Dogs have also been trained to detect diabetes on breath. **UPDATE ** A company called Breathlink has a breath sampling device that is currently (May 2015) undergoing clinical trials to detect breast cancer and lung cancer. Another company Owlstone is similarly trialing a device to detect lung cancer. More on smell and health in my website.

Is NEW CAR smell dangerous? What is that "new car" smell? Why do manufacturers go to great lengths to manufacture it? The Ecology Center identified more than 275 chemicals, some of which are associated with allergies, birth defects, impaired learning, liver problems, and cancer.

Perfume ban - The Scientific Committee on Consumer Safety (SCCS) advised the European Commission to restrict citral, found in lemon and tangerine oil, along with coumarin, found in tropical tonka beans, and eugenol, found in rose oil and about 90 other perfume ingredients. Chanel No. 5 would have disappeared as would many other famous brands. This proposed ban stemmed from fears about skin allergies. Perfumers (and most people of good sense) were outraged. The word was that the SCCS was flexing its muscle having been ignored by the International Fragrance Association (IFRA). However, a new set of EU guidelines has been issued that scales back the rather extreme recommendations of the SCCS.

1 comment:

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