Parosmia, a condition in which smells are distorted, has been documented since 1895 and affects up to 5% of the general population. The cause of parosmia can range from sinonasal diseases, viruses, surgeries, traumatic brain injury, and toxic chemicals, to neurological and psychiatric conditions, and medications. With the COVID-19 pandemic, parosmia has seen a surge in cases, linked to changes in brain structure following infection.
Recent research has shown that parosmia patients are mainly triggered by certain substances, including thiols and pyrazines. In 2015, the "olfactory training" regimen was improved to more effectively treat post-infectious olfactory loss and was named "modified olfactory training" (MOT). In 2022, it was found that MOT is also effective against COVID-19-induced parosmia.
The evaluation of parosmia is done using a variety of methods, including smell identification tests, surveys, fMRI, MRI, PET/CT, and gas chromatography. Treatment for parosmia can vary in duration, which makes it important to focus not only on helping patients regain a normal sense of smell but also on supporting them through their recovery journey.
Phantosmia is the distortion of smells that occurs in the absence of olfactory stimuli, with etiologies ranging from infections and traumatic brain injury to psychiatric disorders like schizophrenia. Unlike parosmia, the treatment of phantosmia is less straightforward, with an emphasis on determining the cause and providing symptomatic relief.
The review of parosmia and phantosmia highlights the need for continued research into these debilitating conditions to better understand their causes and provide more effective treatments for the millions of people affected. By educating the public and health professionals about these conditions, we can help those with parosmia and phantosmia lead happier, more fulfilling lives. Through better understanding, support, and care, those suffering from these qualitative olfactory disorders can be given the help they need to manage their symptoms and improve their overall quality of life.
The paper can be found here.
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