Long Covid undermines the quality of life for many people. For some individuals, the debilitating illness manifests as changed senses of smell and taste. A new study adds light on the mechanism that may produce Parosmia – common sequelae of smell loss associated with covid-19 – or odor misperception.
Long Covid, or COVID-19 symptoms that last long after the initial infection is gone, is a problem for a large number of people. It’s difficult to estimate the scope of the problem. Similarly, the mechanisms at work are unknown. A new study investigates the latter, focusing on parosmia, a distinctive symptom of long Covid.
Although parosmia, or a distorted sense of smell, is not unique to the pandemic, it rose to prominence as Covid messed with people’s senses of smell.
When you smell coffee, you can detect if you have this condition.
People with parosmia can find the smell of freshly ground coffee as disgusting as the smell of trash on fire.
Researchers have now found why some foods and beverages smell (and possibly taste) awful to individuals with parosmia.
In a new study that was published in the journal Communications Medicine, a group of scientists found that certain highly potent smell molecules in coffee cause the disgust that comes with parosmia.
Take, for example, 2-furanmethanethiol, the most powerful aroma molecule you’ve never heard of. It’s one of those compounds that’s been driving people insane for a long time.
The team was able to test coffee constituents on volunteers who experienced parosmia and compare their reactions to those who did not by capturing the aroma of coffee.
People with parosmia can identify the unpleasant aroma molecules in coffee.
Scientists discovered 15 widely identified substances that caused parosmia among the 29 volunteers.
“This is solid evidence that it’s not all “in the head”, and that the sense of disgust can be related to the compounds in the distorted foods,” explained Dr. Jane Parker, Associate Professor of Flavour Chemistry and Director of the Flavour Centre at the University of Reading.
Adding: “The central nervous system is certainly involved as well in interpreting the signals that it receives from the nose. The parosmic experience is a combination of the two mechanisms which produces the distorted perception of everyday foods, and the associated sense of disgust.
“We can now see that certain aroma compounds found in foods are having this particular effect,” says the researcher. It will, we hope, be reassuring for those with parosmia to know that their experience is “real”, that we can identify other foods which may also be triggers and, moreover, suggest “safe” foods that are less likely to cause a problem. This research provides useful tools and strategies for preventing or reducing the effect of the triggers.”
“We still have a long way to go in understanding this condition,” said Mr. Simon Gane of the Royal National Ear, Nose and Throat and Eastman Dental Hospital, one of the researchers, “but this research is the first to zoom in on the mechanism in the nose.
“We now know this has to be something to do with the nerves and their receptors because that’s how these molecules are detected.”
The following are some of the most commonly mentioned foods and beverages that cause parosmia in sufferers:
- Coffee
- Onions
- Garlic
- Chicken
- Green peppers
A method called GC-Olfactometry was used in the study. A capillary is a long and narrow conduit that collects the scent of the coffee.
Some of the compounds that make up smells move through the capillary more quickly than others.
The fastest ones emerge first from the opposite end, followed by the slower ones, separating the compounds and allowing the volunteers to smell and describe them one by one.
Prior to the global pandemic caused by COVID-19, parosmia was an uncommon ailment that only occurred after infections like the common cold, flu, or sinus infections, with little knowledge of the disease’s causes and remedies.
COVID-19 symptoms included loss of smell and taste in 50-60% of individuals during the pandemic, with about 10% developing parosmia.
While the loss of smell and taste has grown less common since the Omicron variant (expected to occur in roughly 10%-20% of instances) and parosmia cases are likely to be fewer, parosmia is still thought to afflict millions.
Long Covid can also be identified by the following signs:
- Extreme exhaustion (fatigue)
- Breathing problems
- Pain or tightness in the chest
- Memory and attention problems (“brain fog”)
- Sleeping problems (insomnia)
- Palpitations in the heart
- Dizziness
- Stitches and pins
- Joint discomfort
- Anxiety and depression
- Earaches, tinnitus
- Irritable bowel syndrome, diarrhoea, stomach aches, and a loss of appetite
- A fever, cough, headaches, and a painful throat
- Rashes.
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