Smells Like Covid Part 2

It's been a couple years since the world learned the word "anosmia," so here's some updates:

(but don't forget this post about how parosmia worked with covid)

The first mass screening system for COVID cases has been developed with a sensitivity of 97%

Dec 2022, phys.org

https://medicalxpress.com/news/2022-12-mass-screening-covid-cases-sensitivity.html

Washing your hands with hydroalcoholic gel, smelling it and using a QR code to answer a short questionnaire. These very simple actions make up the world's first patented mass screening system for COVID cases.

Citrus fruits and apples are two of the first aromas that people with the SARS-CoV-2 virus stop detecting.

"Citrus" -- I don't remember seeing this at all, so I looked further into the report: "Based on the literature and habits of our Mediterranean study population, it was determined that the most suitable odoriferous substance was lemon." via Institute for Research in Fundamental Sciences in Iran and R DOty at U Penn: Moein, S. T. et al. Smell dysfunction: A biomarker for COVID-19. Int. Forum Allergy Rhinol. 10, 944–950 (2020). https://pubmed.ncbi.nlm.nih.gov/32301284/  -- This study used the University of Pennsylvania Smell Identification Test (UPSIT) which has 40 odorants; I can't read the paper because paywall, but I guess "citrus" or "lemon" is one of those odors. The paper wasn't meant to find the most prevalent non-detectable odor, but I guess it was just sitting there in the data?

"The antigen tests on the market have an average sensitivity of 80%, which means that the number of false negatives is 20%. What we have developed is not a diagnostic test, but a screening system that aims to detect the maximum possible number of positives and prevent false negatives," explained the researchers.

via Youcef Azeli et al, A machine learning COVID-19 mass screening based on symptoms and a simple olfactory test, Scientific Reports (2022). DOI: 10.1038/s41598-022-19817-x

https://dx.doi.org/10.1038/s41598-022-19817-x

Image credit: Stainless steel climate chamber at the Technical University of Denmark, Mikal Schlosser, 2022

Loss of smell following COVID linked to a person's immune reaction to the infection

Dec 2022, phys.org

https://medicalxpress.com/news/2022-12-loss-covid-linked-person-immune.html

They studied antibody levels in people infected during the early days of the pandemic—in all, they studied blood samples of 306 people who had donated blood for study after recovering from a COVID-19 infection. In comparing the antibody levels with other data provided by the donors and their doctors, the researchers determined that those people who had higher antibody levels tended to be the same people who had reported losing their sense of smell or taste. They found that such patients were twice as likely to lose one or the other sense as those who did not have higher-than-average levels of antibodies in their blood.

via Columbia University Irving Medical Center, the University of Pennsylvania, the National Institute of Alcohol Abuse and Alcoholism and the New York State Psychiatric Institute: Jonathan B. Overdevest et al, Chemosensory deficits are best predictor of serologic response among individuals infected with SARS-CoV-2, PLOS ONE (2022). DOI: 10.1371/journal.pone.0274611

https://dx.doi.org/10.1371/journal.pone.0274611

Scientists find key reason why loss of smell occurs in long COVID-19

Dec 2022, phys.org

https://medicalxpress.com/news/2022-12-scientists-key-loss-covid-.html

The reason some people fail to recover their sense of smell after COVID-19 is linked to an ongoing immune assault on olfactory nerve cells and an associated decline in the number of those cells, a team of scientists led by Duke Health report.

via Duke University Medical Center: John Finlay et al, Persistent post-COVID-19 smell loss is associated with immune cell infiltration and altered gene expression in olfactory epithelium, Science Translational Medicine (2022). DOI: 10.1126/scitranslmed.add0484.

https://dx.doi.org/10.1126/scitranslmed.add0484

Post Script:

Nasal injections could treat long-term COVID-19–related smell loss

Jan 2023, phys.org

https://medicalxpress.com/news/2023-01-nasal-long-term-covid-19related-loss.html

Using injections of platelet-rich plasma derived from a patient's own blood. In a trial of 26 participants, those who received the treatment were 12.5 times more likely to improve than patients who received placebo injections. 

"It's a nerve damage and nerve regeneration issue that we're dealing with," she said.

via Stanford: Carol H. Yan et al, Use of platelet‐rich plasma for COVID‐19–related olfactory loss: a randomized controlled trial, International Forum of Allergy & Rhinology (2022). DOI: 10.1002/alr.23116

https://dx.doi.org/10.1002/alr.23116

Exobiotic Nose Patrol

Smelling your lover's shirt could improve your sleep

Feb 2020, phys.org

"Romantic Partner" they call it.

155 people, sweaty t-shirts, you get the idea.

You don't even have to be there, just your shirt: "effect similar to taking oral melatonin supplements."

-University of British Columbia Department of Psychology

I'm going to chime in here and say this is something to do with security and familiarity. Knowing that another member of your tribe is with you while you sleep makes you less paranoid of the silent creepers waiting to attack you in the dead of night, be they lions, tigers or viruses. And your body knows who is a member of your tribe via both olfaction and your immune system (which are inter-related by their chemosensing inputs).

Your immune system knows who's deep inside your network because their microbes are deep inside your body crawling and growing and metabolizing all over your face, in your nostrils, under your fingernails, and throughout the entire length of your digestive system. Your immune system has one job, and that's to keep the xenobiotics at bay.

Yes, your immune system is hyper xenophobic. As you move through life, you pick up all kinds of microbes from your environment and especially from the people around you. All the while your immune system is working like crazy to detect, attack and remove all those microbiological trespassers.

If you spend enough time with certain people, then your immune system will need a way to identify those people and their biomes so that it doesn't waste time attacking things that aren't actually a threat. It's a probability game -- if you hang out with these people a lot, then they probably aren't a threat, and neither are their microbodies; you'd be better off saving your energy for another time, like when you're at the gym swimming in a sweaty soup of other people's effluence.

Point being, the more immunologically exposed you are to another person, the more your immune system will "know" who they are by the way they smell, and even while you sleep. And when your immune system is relaxed, so are you. (And yes, immunological exposure means exactly what it sounds like.)

Image source: Dartmouth College Electron Microscope Facility

Post Script

The “exposome” revealed - a barrage of bacteria, chemicals, microscopic animals and more

Stanford Medicine, Sep 2018

For two years straight, Michael Snyder, MD, professor and chair of genetics at Stanford, sported a peculiar accessory — a little gray box strapped to his bicep taking sips of air and recording his exposome cloud.

It turns out, at any given time, we are bombarded by a combination of microbes, fungi, chemicals, viruses, particulates and even tiny microscopic animals, a new paper in Cell reported. This whirling plume of particulates is called the human exposome.

The long-term goal, Snyder said, is to simplify the device into something that resembles an exposome-monitoring smart watch that can suck up and analyze the atmosphere on its own.

 

On Allergies and Sensitization

Writing about smell will get you thinking about nuisance odors and about folks who think that smells are making them sick. A lot of this has to do with allergies, and allergies can be a tricky thing. There is no threshold for the amount of a thing that will elicit a reaction, and so allergies tend to be modulated by our own minds, at least to some extent. In other words, if you’re stressed, or if you’re thinking way too much about these allergies and their allergens and the environment where they come from, you may amplify the effects, and you may start sneezing or scratching at the most miniscule of exposures.

The way allergies work in the body is pretty damn confusing. There’s different kinds of allergies, some are hardwired, we might say, and some are ‘learned’ by the body. Some allergies can be deadly, like a shellfish allergy that closes your throat. Some can be just annoying, but won’t kill you or send you to the hospital (unless your body gets so hijacked by your own histamines that you smash your head into a wall).

All this being said, when I came across this short explanation on how allergies work, and I found it to be somewhat comprehendible, I thought I should repeat it here.

Most chemicals and their metabolic products are not sufficiently large enough to be recognized by the immune system as a foreign substance and thus must first combine with an endogenous protein [something that comes from inside the body not outside, endo- vs exo-] to form an antigen (or immunogen). Such a molecule is called a hapten. The hapten-protein complex (antigen) is then capable of eliciting the formation of antibodies. Subsequent exposure to the chemical results in an antingen-antibody interaction, which provokes the typical manifestations of allergy that range in severity from minor skin disturbance to fatal anaphylactic shock.

-Essentials of Toxicology, Casarett and Doull

Got all that? The “allergic reaction” is really an antigen-antibody reaction. It is your body fighting an intruder, and you are the collateral damage.

***

Please take a look at another post called The Dangers of Smell and Perfumes in the Workplace but it’s based on this article: perfume in the workplace, which is an interesting look inside the work of an HR worker who has to deal with employees complaining about their smelly coworkers, and soothing the hypersensitive worker who thinks their coworker’s perfume is making them sick (it’s not; unfortunately, it’s your own mind doing that).