Science

Researchers Suggest Best Treatment for Loss of Smell Due to COVID-19

Among the long-term effects of COVID-19 is the more or less marked loss of smell. While some people complain about it for a few weeks before making a full recovery, others say they never fully regained their olfactory abilities several months after infection.

How to recover the sense of smell after months of dysfunction? Some have resorted to steroids to help them with this, but their use is controversial and is not without side effects. Olfaction experts offer a simple and natural way to gently, but surely, recover that precious sense after COVID-19. How? ‘Or’ What ? By re-training the nose to smell certain odors. This therapy is called olfactory rehabilitation.

This is a long task that could take months, but smelling at least four different aromas twice a day could help recover faster and more fully without side effects. This recommendation is based on a systematic, evidence-based study, which at the same time concluded that corticosteroids should not be the first treatment option for loss of smell due to COVID-19.

These drugs are commonly prescribed to treat nasal congestion and inflammation, but this does not appear to be the cause of odor dysfunction in people with COVID-19, especially if the loss of smell persists long after the condition has healed. initial infection. Corticosteroids may therefore be ineffective.

According to the researchers, olfactory training, on the other hand, is a more effective way to restore the nose after a viral infection. ” As a group of experts, we strongly insist on the initial consideration of olfactory training », They write in their document. ” Scent training has no known side effects and is inexpensive. Plus, it’s the only treatment available… backed by a solid evidence base “.

Proven effectiveness

While it is difficult to compare steroid and scent training treatments for post-COVID-19 olfactory dysfunction specifically because no controlled studies have been done, the idea of ​​scent training has been around for some time. It has even been used successfully to help treat loss of smell due to other infections.

In 2020, for example, a systematic comparison of potential treatments for post-viral loss of smell – including scent training, systemic steroids, topical therapies, non-steroidal oral medications, and acupuncture – found that olfactory training should be the number one recommendation based on current evidence of effectiveness.

Especially since today we may need to implement this practice on a scale never seen before. In fact, about 60% of people who contract COVID-19 experience a disturbance in smell, while about 10% experience symptoms that persist for weeks or even months. Fortunately, it seems that for most people the sense of smell does come back little by little, and smell training could have something to do with it.

In early 2021, a study of 1,363 coronavirus patients with olfactory dysfunction found that 95% of patients had regained their sense of smell after six months. These patients had been advised to undertake two scent training sessions per day at home, although it is not clear how many people actually followed these recommendations. The results were published in the journal International Forum of Allergy & Rhinology.

Corticosteroids: lack of evidence of efficacy and side effects

Corticosteroids have also been considered as a treatment option, but this drug is not without side effects: fluid retention, high blood pressure, mood swings, to name a few. In addition, it may not be of any use. The researchers point out, however, that at this time, we do not have enough evidence to be sure and therefore exclude it completely from treatment options. Although some case reports suggest that steroids may help people who have lost their sense of smell after COVID-19, if left unchecked, it is not known whether these patients would have recovered on their own.

Based on the current evidence, the authors join many other experts who call for caution: “ until randomized, placebo-controlled trials can be undertaken, we should start with scent training and not steroids “.

Recovery of smell by stimulating neuroplasticity

[L’entraînement de l’odorat] emerged as a cheap, simple, and side-effect free treatment option for a variety of causes of loss of smell, including COVID-19 Explains Carl Philpott of the University of East Anglia, UK. ” It aims to promote recovery by relying on neuroplasticity – the brain’s ability to reorganize itself to compensate for a change or injury “.

Representation of the olfactory bulb and human olfactory nerves (in yellow). During a viral infection, the nerves can be damaged more or less severely. In this case, the recovery is slow because it involves the regeneration of olfactory nerve cells by the stem cells still present and, following this, the re-education of the brain to interpret these new connections. © Wikimedia Commons / Patrick J. Lynch / CC BY 2.5

It takes time, and not everyone will improve at the same rate. Older people, for example, may take longer to regain their sense of smell because they have fewer olfactory receptor neurons. Traditionally, scent training has relied on four scents: clove, rose, lemon, and eucalyptus, but which one doesn’t really matter.

It may even be beneficial to focus on familiar smells, like perfumes, lemon zest, vanilla, or ground coffee, and reflect on memories as they are sniffed. For best results, it is advisable to change the four benchmark “smells” every 12 weeks.

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