Loss of smell and taste

[forestglip]

I just made the connection that maybe my life-long poor sense of smell and taste is related to ME/CFS. It's common in acute and long COVID, so maybe I have a subtype that is somehow similar to those with LC.

Anyone else with non-COVID-related ME who has long-term profound lack of smell and/or taste?

 

[Peter T]

I have had ME for some 30 years but it did not impact on my sense of taste or smell for most of that time. Over the last eight years, when my ME has been significantly more severe I have noticed that the scent of the flowers in my garden, partly planted for fragrance, has markedly faded. For a while I kept saying to myself these modern varieties have poorer fragrance until I realised it was me.

I have not had Covid, and I have no idea if this is ME or age related (am in my 60s).

Note, as not had Covid have not done the poll.

 

[forestglip]

Note, as not had Covid have not done the poll.

Oh sorry, I should change the wording. I should have said "before COVID pandemic" to rule out the possibility of those who got it from COVID. Meant for anyone that has anosmia and ME and knows it's not caused by COVID.

 

[forestglip]

COVID-19–related anosmia is associated with viral persistence and inflammation in human olfactory epithelium and brain infection in hamsters

In four patients who developed persistent loss of smell, the authors detected lasting SARS-CoV-2 presence in the olfactory mucosa, suggesting that the prolonged relapsing anosmia in patients with COVID-19 could be due to persistent viral infection.

 

[forestglip]

Thread about loss of smell on Phoenix Rising where a couple people say their anosmia started around the same time as ME.

 

[forestglip]

Olfactory bulb involvement in neurodegenerative diseases,
Johannes Attems et al, 2014 Apr

Olfactory dysfunction is a common and early symptom of many neurodegenerative diseases, particularly of Parkinson's disease and other synucleinopathies, Alzheimer's disease (AD), and mild cognitive impairment heralding its progression to dementia. The neuropathologic changes of olfactory dysfunction in neurodegenerative diseases may involve the olfactory epithelium, olfactory bulb/tract, primary olfactory cortices, and their secondary targets. Olfactory dysfunction is related to deposition of pathological proteins, α-synuclein, hyperphosphorylated tau protein, and neurofilament protein in these areas, featured by neurofibrillary tangles, Lewy bodies and neurites inducing a complex cascade of molecular processes including oxidative damage, neuroinflammation, and cytosolic disruption of cellular processes leading to cell death. Damage to cholinergic, serotonergic, and noradrenergic systems is likely involved, since such damage is most marked in those diseases with severe anosmia. Recent studies of olfactory dysfunction have focused its potential as an early biomarker for the diagnosis of neurodegenerative disorders and their disease progression. Here, we summarize the current knowledge on neuropathological and pathophysiological changes of the olfactory system in the most frequent neurodegenerative diseases, in particular AD and synucleinopathies. We also present neuropathological findings in the olfactory bulb and tract in a large autopsy cohort (n = 536, 57.8 % female, mean age 81.3 years). The severity of olfactory bulb HPτ, Aβ, and αSyn pathology correlated and increased significantly (P < 0.001) with increasing neuritic Braak stages, Thal Aβ phases, and cerebral Lewy body pathology, respectively. Hence, further studies are warranted to investigate the potential role of olfactory biopsies (possibly restricted to the olfactory epithelium) in the diagnostic process of neurodegenerative diseases in particular in clinical drug trials to identify subjects showing early, preclinical stages of neurodegeneration and to stratify clinically impaired cohorts according to the underlying cerebral neuropathology.

 

[forestglip]

Hypothesis: Since loss of smell comes on so quickly in people who get the COVID infection, and goes away as soon as the infection is gone, and can persist in Long COVID, maybe this points to the virus directly causing anosmia and continuing to stick around to cause it in LC.

Viral persistence has already been suggested as a theory. But if it's true, and anosmia being a direct effect of viral load is true, maybe anosmia can be used as a non-delayed marker of viral levels. It might be very hard to tell if a treatment is helping or hurting by measuring standard ME symptoms like PEM because they seem to be fairly delayed from an initial infection, so effects would likely be delayed from the removal of the infection as well.

But if a treatment is helping to decrease COVID or another virus, it presumably might quickly also improve sense of smell, since that's what we see at the end of normal acute infection. If we see improvements in smell, that could give a reason to at least continue this treatment for a couple months to see if improvements in ME follow.

I'm planning a DIY anosmia metric. I'll fill up around 30 jars with an odorless solvent, and each one will have a different concentration of some pungent chemical, like vanilla or cinnamon. Going from so little that it's impossible to smell to so much it's obvious. And I'll regularly take a whiff from them all and record the lowest that I was able to definitely smell. (I'll also randomize the jars, hide the labels, and have a few with no chemical at all, to make this test a bit more reliable.) This should allow noticing much smaller changes in sense of smell than I can notice normally.

Maybe I'll do this every day and see if I notice any changes when I add various supplements.

 

[Peter T]

Since loss of smell comes on so quickly in people who get the COVID infection, and goes away as soon as the infection is gone, and can persist in Long COVID, maybe this points to the virus directly causing anosmia and continuing to stick around to cause it in LC.

Can we say it goes away as quickly? I know of one person whose loss of smell persisted for at least a year after he acute phase even though in all other aspects he was recovered, working full time, running marathons and an active social life.

 

[Jonathan Edwards]

Loss of smell/taste from drugs and infections often continues long after the cause has gone. My understanding too is that is often the case for Covid.

 

[EndME]

I wanted to point of that the interesting Blood-brain barrier disruption paper evaluated ansomia via testing (Q-SIT-based method). I recall that anosmia was very highly present in the study by Wüst et al, at 12% of the cohor, probably even overrepresented and that people with ansomia didn't improve in that rather weird and probably useless monoclonal antibody paper by Klimas et al.

There have been some long-term follow-up papers for loss of smell and taste after Covid, for instance Long-Term Taste and Smell Outcomes After COVID-19 and in those loss of smell tends to be more persistent than loss of taste. Hard to judge if those papers are really robust but it possibly means one shouldn't shovel loss of smell and loss of taste under one thing (via and/or), but rather that one should keep them separate.

 

[EndME]

Can we say it goes away as quickly? I know of one person whose loss of smell persisted for at least a year after he acute phase even though in all other aspects he was recovered, working full time, running marathons and an active social life.

Especially with the very early Covid variants this seemed to have been rather common.

Hypothesis: Since loss of smell comes on so quickly in people who get the COVID infection, and goes away as soon as the infection is gone, and can persist in Long COVID, maybe this points to the virus directly causing anosmia and continuing to stick around to cause it in LC.

From an epidemiological stand-point it will also be hard to seperate loss of smell is quick to resolve after Covid but not in LC since all studies consider that someone that has loss of smell to be a LC patient (whether that is a sensible classification is a different matter). So nothing suggests that one resolves quicker than the other and I don't think anosmia is more commonly reported in the more syndromic versions of LC such as ME/CFS vs the non-sydromic versions (in fact given the nature of the definition the opposite is more likely to be true).

Personally I had loss of smell/taste for several months after my first Covid infection which was then followed up by glandular fever, but at no point in time would I have considered myself to have ME/CFS. Similarly several of my friends were perfectly healthy despite not being able to smell anything for months. Whilst in later Covid infections with later variants loss of smell/taste was only very short but I've been still struggling with the after effects of those infections for years.

 

[forestglip]

Can we say it goes away as quickly? I know of one person whose loss of smell persisted for at least a year after he acute phase even though in all other aspects he was recovered, working full time, running marathons and an active social life.

Loss of smell/taste from drugs and infections often continues long after the cause has gone. My understanding too is that is often the case for Covid.

Oh that's unfortunate, I guess my memory about this was wrong.

But there are some for whom it goes away pretty quickly, right? If so, it's conceivable that using anosmia as a fast marker of LC might work in at least some people.

It'd be great to find data on the timelines of people who had anosmia and recovered from LC: i.e. how long before or after recovery did their sense of smell return.

But also, I wonder if there are other possible relevant markers that do normally go away very quickly after acute COVID and tend to stick around in LC.

 

[rvallee]

More like the opposite, where several times I had periods of very heightened smell sensitivity. It's still a bit there but not as bad.

 

[Kitty]

More like the opposite, where several times I had periods of very heightened smell sensitivity. It's still a bit there but not as bad.

This!

Mine taste and smell has always been so acute that it's a problem, but there've been periods in ME where it's got even worse.

I kept half-wishing I'd get anosmia after Covid, because just for once I'd be able to eat normal food and use a public toilet at an event where people would be applying perfume. Had it twice, though, and it's made no difference at all.

 

[NelliePledge]

More like the opposite, where several times I had periods of very heightened smell sensitivity. It's still a bit there but not as bad.

Yes not very heightened but i definitely have a strong sense of smell and sometimes pick up smells that don’t appear to have a source.

 

[forestglip]

Patients with COVID-19-associated olfactory impairment also show impaired trigeminal function

Olfactory dysfunction is one of the most common symptoms of COVID-19 and has been described numerously in the literature. COVID-19-associated olfactory loss is characterised by a rapid onset and improvement after a short time in about half of patients. However, in about 50% of patients, a reduction in olfaction can be measured even after three months. Olfactory function improves in most patients during the course of the disease, but in some patients limitations of the olfactory function can be measured even 6 months after the disease.

One interesting thing I've learned is that there are two main "smell" systems: olfactory and trigeminal. Olfactory are more typical smells, like foods. Trigeminal sensations are caused by irritating chemicals like menthol or alcohol.

And I do smell things like alcohol and acetone much better than smells like cinnamon or vanilla. For the above home experiment, I bought a bottle of vanilla extract. But it turns out 41% of the liquid is alcohol, and when I take a whiff of the concentrated liquid directly, 90% of what I smell is alcohol. So I'm thinking to use ground cinnamon instead.

Another paper about trigeminal sensory features in COVID:

Trigeminal features in COVID‐19 patients with smell impairment

To date, few papers have studied trigeminal nasal sensation in COVID‐19 patients with smell reduction. Moreover, when nasal chemesthesis was investigated, it was assessed together with olfaction in a bimodal stimulation, possibly reducing the accuracy of the results. 3 As recently demonstrated by Parma et al., 4 our data confirmed a high rate (56.6%) of severe reduction of nasal chemesthesis in COVID‐19 patients with olfactory dysfunction. Our data show that trigeminal nasal sensation resolved in a high percentage of patients after 6 months of follow‐up, similarly to the recovery rate of olfactory perception. 5

Remarkably, self‐reported severe impairment of trigeminal nasal sensation at the diagnosis was associated with a lower rate of olfactory recovery at 6‐month follow‐up, highlighting the potential role of trigeminal nasal function as a predictor of smell recovery. These self‐reported data were further investigated with menthol stick identification test, which represents a unimodal trigeminal stimulation; almost all patients with anosmia at the Sniffin’ Sticks Test failed to identify menthol.

I thought I had seen a study showing olfactory, but not trigeminal, was primarily affected in COVID anosmia, but now I can't find it.

 

[Kitty]

One interesting thing I've learned is that there are two main "smell" systems: olfactory and trigeminal.

Both of mine must be maddeningly over-enthusiastic then.

I spent years reporting a really strong smell of gas that I picked up every time I passed a disused church, but no one else could detect it. After numerous emergency callouts I had to give up; I was still in my teens, and the gas company thought I was a prankster. They refused to come out again because none of their trained personnel had been able to smell it.

Until someone started work on renovating the church, smelt gas inside, and called out the transmission company. They discovered a damaged pipe and enough gas built up in the undercroft to blow up half the street. I was turned back on my way to work by police, who said they'd had to evacuated the whole area—they were a bit surprised when I said I'd been reporting the leak for three years and had just been told to stop annoying them.

 

[forestglip]

Both of mine must be maddeningly over-enthusiastic then.

I spent years reporting a really strong smell of gas that I picked up every time I passed a disused church, but no one else could detect it. After numerous emergency callouts I had to give up; I was still in my teens, and the gas company thought I was a prankster. They refused to come out again because none of their trained personnel had been able to smell it.

Until someone started work on renovating the church, smelt gas inside, and called out the transmission company. They discovered a damaged pipe and enough gas built up in the undercroft to blow up half the street. I was turned back on my way to work by police, who said they'd had to evacuated the whole area—they were a bit surprised when I said I'd been reporting the leak for three years and had just been told to stop annoying them.

I can't seem to find an actual source (where I can understand the technical language) about whether mercaptan, the smelly chemical added to natural gas, works primarily through olfactory or trigeminal, but the AI Claude seems sure it's olfactory, though of course it could be wrong:

The additive that gives natural gas its distinctive smell primarily works through the olfactory system. The most common odorant used in natural gas is tert-Butylthiol (t-butyl mercaptan), which has a strong, unpleasant odor that can be detected by the human nose at very low concentrations.

When this odorant enters the nose, it binds to olfactory receptors in the nasal cavity. These receptors send signals to the olfactory bulb in the brain, which then relays the information to other areas of the brain for processing and interpretation. This allows us to perceive the characteristic smell and identify it as natural gas.

While some odorants can stimulate the trigeminal nerve, which is responsible for sensations like burning, cooling, and irritation in the nose and mouth, the primary mechanism for detecting the added odorant in natural gas is through the olfactory system. The trigeminal system may play a secondary role, but it is not the main pathway for detecting the smell of natural gas.

 

[Kitty]

That wouldn't surprise me, I imagine it's more the volatile chemicals that activate the trigeminal system. I could also detect those in very small concentrations, and they still make my eyes stream and my throat sore.

Luckily age has knocked some of the acuity off my smell/taste system. Not enough to allow me to eat the range of foods most people can tolerate, though, many still taste so overwhelmingly strong that it's absolutely revolting to me (like fish) or the smell causes nausea and vomiting (like vinegar and some cheese).

 

[forestglip]

Preparation for my DIY anosmia test has begun!

Here are my notes on how I prepared various concentrations of cinnamon in water:

1/2 tsp ground cinnamon
100 mL water

Blend solution in magic bullet to make particles smaller to stay suspended longer.

Use eye dropper and add multiples of 4 drops of cinnamon mixture to each test tube, from 4 drops to 60 drops.

Fill the remaining space in each test tube with water up to the bottom of the threads.

Fill five tubes with plain water to act as controls.

Label lids with number of drops.

I was trying with ground coffee and cinnamon. Ended up going with cinnamon, but I think coffee would have worked.


Test tubes filled with various numbers of cinnamon solution drops.

Reenactment of adding cinnamon solution.

All test tubes filled with solution, topped off with water, and labeled. All activity supervised by cat.

I plan to randomize the order before each test session by mixing tubes up in a hat. Then I'll close my eyes, pull them out one by one, shake them to get the particles evenly distributed, then smell. If I detect cinnamon, I place it on the right side of the table, if not, left.

Cinnamon and coffee quickly settle to the bottom of water. Have to shake immediately before any transfer of liquid (e.g. when using eye dropper). Would be nice to have a smelly chemical that stays suspended or a thicker solvent for cinnamon or coffee which keeps the powder suspended.

A liquid chemical with a powerful scent which dissolves fully in water would be ideal. Was also considering essential oils.

Not sure how much "smell fatigue" will factor into smelling many tubes in a row. Smell fatigue meaning to get more numb to a particular smell immediately after smelling it.

Test tubes I bought on Amazon

I'm not exactly sure what my testing protocol will be. Maybe just twice a day, once in the morning, once in the evening. Maybe go through the whole set of tubes more than once at each session to be more accurate.

And I'll record all the ones I detected and those I didn't.