Post-COVID infection, did your coffee smell like garbage? Now, scientists have found the reason behind this. Researchers from the School of Chemistry, Food and Pharmacy, University of Reading, and the University College London Hospital have tried to understand the underlying mechanism and found the trigger molecule behind 'parosmia', a debilitating condition in which familiar smells become distorted and disgusting.
"We found that specific highly odour-active molecules are the cause of parosmia in most cases, and initiate the sense of disgust, suggesting that parosmia is, at least in part, a receptor-level phenomenon," say the authors, whose study published in Communication Medicine Journal.
For the study, researchers showed 15 different molecular triggers of this symptom. The highly potent odour molecule that triggers the condition is called '2-furanmethanol', which is found in coffee. While people with a normal sense of smell identified this smell of the molecule as coffee or popcorn, those with parosmia called it 'dirty', like sewage or garbage.
The study used a technique that separates the chemicals that make up the smell of instant coffee, and let several people with parosmia after infection smell them one at a time. "Most of these people picked out the same chemicals as smelling disgusting, and setting off their parosmia," the authors said.
These chemicals are known to smell strong to humans, and can be grouped into four classes, based on their chemical shape and elements they contain.
Agreeing that this condition is being seen in many patients even now, Dr Satyanarayana Mysore, Pulmonologist, HoD, Sleep Medicine, Manipal Hospital said, "There have been many patients who recovered from this condition about three to four weeks after the COVID-19 infection. But there are a few who have parosmia and continue to complain of feeling disgusted with certain foods, affecting their diet."
However, he says this is not a condition limited to COVID-19, and parosmia had existed earlier too. Other infections or certain neurological diseases affecting the nervous system are associated with this condition, he explains. He says in COVID-induced parosmia, "one thing is people who have had atrophic rhinitis or people who had loss of smell due to local battles being fought at the level of nose using IgG antibodies, there will be disruption of the nerve endings which gives the perception of sense of loss of smell or distorted smell".
The authors of the study intend the findings to help in understanding which chemical compounds trigger this condition, and the study aims to help in developing diagnostics and therapies for this condition in future.
