One of the most frequent symptoms during COVID-19 is loss of smell or taste. Although these symptoms might be considered mild or moderate, they actually have a huge impact on people’s quality of life, especially if they last for weeks after infection. But what options do these patients have?
Anosmia: loss of smell
The loss of smell that can appear after an infection caused by SARS-CoV-2 usually lasts a few days or weeks after the onset of symptoms. However, in some patients , this symptom may remain even when the virus has been completely eliminated from the body.
When this or any other symptom that appears during the infection is still present twenty-eight days after the start of the disease, we speak of persistent COVID or Long COVID, in English.
Within the range of symptoms that can remain during persistent COVID, the loss (anosmia) or reduction (hyposmia) of smell can be a great detriment to people’s quality of life.
We have all suffered at some time in our lives from a strong cold that does not allow us to perceive any smell and that even affects us when eating. Let’s imagine that this sensation lasts for weeks, without knowing when it will recover.
A study in COVID-19 patients revealed that 47.85% suffered from anosmia and that it usually occurs when the disease has milder symptoms, since it is rarely seen in severe patients.
Why lose your sense of smell during COVID-19?
The infection caused by the SARS-CoV-2 coronavirus is carried out through the S protein (from English spike ) of the virus that binds to the ACE2 molecule that is present in some of the cells of our body. Through these molecules, the virus enters the interior of the cell and the infection begins.
Inside the nose, on the roof of the nasal cavity , we find the human olfactory epithelium . In this mucosa we find many types of cells and among them, we have the support cells that present the ACE2 receptor that the coronavirus can use to infect.
Although the function of these cells is not completely understood, they are known to help sensory neurons as structure and support in their function of transmitting olfactory signals. These cells are also known to regenerate slowly but continuously throughout an individual’s life.
A possible mechanism by which anosmia or hyposmia is suffered after COVID-19 is because these cells that help neurons are infected by the coronavirus and it takes time for them to regenerate so that the olfactory epithelium can resume its work.
Other additional or alternative mechanisms, such as virus infiltration of the brain and damage to the olfactory centers , have also been proposed, although this is far less likely . For this reason, olfactory rehabilitation can rule out neurological damage.
In the event that the symptoms persist after recovery from the infection, olfactory rehabilitation can help rule out a neurological sequel and also speed up the process of recovery of smell.
Olfactory rehabilitation post COVID-19
Patients who suffer from anosmia or hyposmia can undergo olfactory rehabilitation that allows us to accelerate the process of smell recovery through a series of simple exercises that can be performed every day, several times a day.
A recently published study has analyzed the practice of this olfactory rehabilitation in 108 articles, and has concluded that this practice is effective and does not entail significant side effects .
The most common way to carry out this rehabilitation consists of four liquid preparations that normally contain substances with the scent of roses, eucalyptus, lemon and cloves . Some clinics may have only three or one of these odorants may be different, but it is recommended that they include fruity, minty, aromatic or floral odorants.
An easy way to do the exercise is to moisten a cotton swab or pad that is commonly used for makeup removal and smell it for twenty to thirty seconds , once before breakfast and once before bed.
These exercises can be performed between twelve and fifty-six weeks , which sometimes presents a problem for patients to adhere to the protocol and perform it in its entirety. To help them follow the protocol and maintain motivation, it is recommended to make a monthly visit to monitor progress and answer questions.
Other interventions that help against anosmia
In addition to olfactory rehabilitation, there are other additional strategies that have been shown to be beneficial in reducing the risk of suffering from anosmia or loss of smell. Exercise in the elderly has been shown to be effective in general and in patients with Parkinson’s. Corticosteroids can also be effective in improving anosmia with an initial dose , although prolonged use has other dangers.
Other practices, including the use of antibiotics , acupuncture , Danggui-shaoyao-san powdered extract, or lipoic acid, do not have sufficient scientific evidence to be considered beneficial for the improvement of anosmia or hyposmia.
References:
Spanish Society of Otorhinolaryngology and Head and Neck Surgery (SEORL CCC). Olfactory rehabilitation offers the best results for the recovery of smell in patients with persistent COVID.
Ojha and Dixit. 2022. Olfactory training for olfactory dysfunction in COVID-19: A promising mitigation amidst looming neurocognitive sequelae of the pandemic. Clin Exp Pharmacol Physiol. doi: 10.1111/1440-1681.13626
Whitcroft and Hummel. 2020. Olfactory Dysfunction in COVID-19. Diagnosis and Management. JAMA. doi: 10.1001/jama.2020.8391
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