The loss of a sense of smell i.e., anosmia and inability to differentiate tastes – ageusia are both widely prevalent symptoms in individuals who test positive for coronavirus infection, right from youngsters to the middle-aged and the elderly. With appropriate medical treatment, a healthy diet and adequate rest, these sensory capabilities gradually improve in most people after 14 to 21 days post the onset of viral infection. However, at times, the SARS-CoV-2 strain of coronavirus lingers in the system for an extended period of 2 – 3 months or more, termed as Long COVID, with afflicted people being called “Long Haulers.”

Also Read: What Is Long COVID? Here Are The Symptoms Of Persistent Coronavirus Infection
Anosmia Or Loss Of Sense Of Smell

In such cases, although the viral load has a decreased pathogenic potential and does not prompt any severe symptoms, it still prolongs the instance of anosmia and ageusia for up to 60 – 90 days, sometimes extending for 6 months. In addition, some of these sick individuals experience a distorted sense of smell too, medically termed as parosmia, wherein items with pleasant smells such as certain fruits, vegetables, spices all have a strong bad chemical-like or even rotten odour. Such patients with mild to moderate symptoms of COVID-19 are advised by doctors to be in home isolation and take prescribed medicines for a full recovery. And to get back their sense of smell, medical professionals recommend practising smell therapy or smell training, to overcome anosmia, as well as the post-COVID occurrence of parosmia.

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What Is Smell Therapy Or Smell Training?

Smell therapy or smell training, also referred to as olfactory training, is not a new procedure formulated recently to resolve anosmia and parosmia in patients with COVID-19. It was actually first described in a research publication in the journal Laryngoscope in the year 2009, by a team of scientists from the University Of Dresden in Germany. They conducted a study on people with smell loss, based on the principle that olfactory function can be influenced and improved by repetitive exposure to various odours.

Also Read: Anosmia: Causes, Symptoms And Treatment

This basic technique of smell training involves sniffing four items with a distinct odour - rose, eucalyptus, lemon, cloves, for 20 seconds, twice a day, for 3 months. People who actively performed smell therapy for the entire period of 12 weeks were able to dispel olfactory dysfunction and enhance their sense of smell. The basis for choosing these specific four items for smell therapy is that just like there exist three primary colours of red, blue and yellow, there are four primary smells – floral i.e. rose, fruity – lemon, aromatic – with cloves and resinous – eucalyptus.

Moreover, while inhaling the odours from these items, people should also try to recollect what those things originally smell like, to engage the memory cells of the brain as well as the nose, which together help to restore olfactory capabilities. In addition, any four items with different smells can be employed while practising smell therapy at home, such as orange, mint, coffee, garlic or a variety of essential oils for example.
Smell Therapy Or Smell Training

How Does This Technique Help Regain Sense Of Smell?

Although the precise biological mechanism of how smell training promotes olfactory potential is not known and yet to be determined, research studies have established some details in this regard.

When we come across a substance with a characteristic smell, the olfactory system processes these odours, which activate the olfactory receptors in the sinuses - cavities located in and around the nostrils. These stimulated olfactory receptors transmit the information via the olfactory nerves right up to the olfactory bulbs in the brain. Within the brain, smells are analysed in the amygdala, cortex, as well as the hippocampus – which is also responsible for memory and emotions.

Thus, smell therapy works by rewiring the brain’s smell-linked nerve channels i.e., the olfactory nerves and repairing damaged olfactory receptors, olfactory bulbs – which happen in COVID-19, which are the organelles that recognise and process smells. This in turn renews memory and emotions associated with distinct odours, thereby helping restore normal olfactory perceptions.

Is Smell Therapy Effective For COVID-19 Patients?

The majority of people affected by coronavirus infection display only mild to moderate symptoms which are dispelled after 14 days - once the viral vector weakens in the body. Likewise, just as they overcome other symptoms of fever, cough, headaches, body pain and fatigue, the loss of sense of smell is also temporary and usually returns once the individual recovers from COVID-19.

However, in many instances, even after effectively combatting coronavirus infection, the afflicted person’s sense of smell does not function at optimal levels and takes weeks or even months to get back to normal. In these situations, practising smell therapy or smell training daily - a simple, cheap, safe method that can be easily done at home, for at least 3 months, or longer if the signs persist, gradually heals and augments the sense of smell, helping to deal with anosmia.