Studies reveal: How corona patients can get sense of smell, taste back

ISLAMABAD: Loss of smell is a strange and distinct feature of COVID-19, so much so that it is considered a better predictor of whether someone has been infected than other common symptoms, such as fever or coughing. Studies suggest that up to half of infected people temporarily lose their ability to perceive smells, although this may be as high as 67% in those with mild to moderate infections – possibly because they tend to be younger, and may be more sensitive to altered olfactory perception, reported international media.

The good news is that various studies have suggested that for people whose olfactory perception has been damaged after a viral infection, repeated short-term exposure to smells can help them to recover.

The way we sense odours is through a cluster of nerve cells called “olfactory sensory neurons”, which are located high up at the back of the nose in a structure called the olfactory bulb. These neurons have tiny hair-like projections which extend out into the mucous-covered nasal lining and respond to odour molecules that we breathe out through our noses.

Early in the pandemic, scientists feared that SARS-CoV-2 might be triggering smell loss by infecting these olfactory neurons and then making its way into the brain, where it might cause lasting damage. Further research revealed that these neurons lack the ACE2 receptors the virus uses to infect cells, but they are found on support cells in the nasal lining which interact with these neurons.

Support act

The job of these support cells – called sustentacular cells – is to maintain the balance of salt ions in the nasal mucus, which the neurons rely on to send signals to the brain. They also provide structural and metabolic support to the olfactory neurons. A recent study in hamsters suggested that it was these support cells that SARS-CoV-2 invaded, rather than the olfactory neurons, and that this prompted a massive infiltration of immune cells, followed by a disruption to the normal organisation of the nasal lining, including the loss of the hairlike projections that the neurons use to detect odour molecules.

The good news is that they also found that the nasal lining began to rebuild itself after around 14 days – although, because it’s difficult to gauge how much a hamster’s sense of smell has returned, it is not clear how long it took them to completely repair the damage.

Lasting damage

Human studies are yielding some answers, however. One recent study, which tracked the health of 2,428 individuals who claimed to have lost their sense of smell and/or taste as a result of COVID-19, found that 40% of them had completely regained their sense of smell six months later, while only 2% reported no improvement at all. A separate survey suggested that recovery may be faster than this for many individuals, with 71.8% reporting a return to “very good” or “good” smell after one month, and 84.2% reporting a return to “very good” or “good” taste.

Loss of taste - another symptom of COVID-19 - is harder to assess, because most studies rely on patients self-reporting their symptoms, and some of what they perceive to be taste loss may be the result of smell loss. Flavour perception is heavily influenced by our sense of smell, which is why holding your nose can make unpalatable foods easier to swallow. However, in the former study of 2,428 individuals, only 3% of them reported that they were still unable to discriminate between sweet, sour, salty, bitter and umami – tastes which are directly sensed by taste buds on our tongues – after six months.

During recovery, some people also report a distorted sense of smell, or “parosmia”. For instance, many people who are recovering from COVID-19 report smelling a foul, rancid odour. Disgusting as this may be, it is usually a sign that your nerve cells are recovering.

Smell training

The good news is that various studies have suggested that for people whose olfactory perception has been damaged after a viral infection, repeated short-term exposure to smells can help them to recover. Smell loss charities recommend picking four scents that you enjoy or have a connection with, and actively sniffing them twice a day, spending around 20 seconds on each scent. Ideally, you should try and pick scents which represent the four categories of flowery, fruity, spicy and resinous – and you could either use essential oils or the actual substance they derive from.

For instance, if you chose lemon as one of your scents, you could use some grated lemon peel. While sniffing the substance, focus your thoughts on lemon and try to recall what your experience of lemon was. It’s not an immediate fix, but over time this should help you to recover your lost sense of smell.

If you’ve lost your sense of smell or taste (or both) to COVID-19, you’re in the majority. Nearly 86 percent of COVID-19 patients lose their ability to smell to some degree and sometimes entirely. The good news? Recent studies show that 95 percent recover these senses within six months of having the illness — most within two to three weeks.

People who lose their sense of smell to any degree or who experience a change in the way they perceive odors are said to suffer from olfactory dysfunction (OD), which also impairs their sense of taste. If you can’t smell anything, you have anosmia. If you can smell odors to some degree but not as well as you normally do, you have hyposmia. And if you can’t taste anything, you have a rare condition called ageusia.

Most people who lose their sense of smell or taste draw the obvious conclusion that something’s wrong with their sensory organs — their nose or sinuses or their tongue or tastebuds. After all, that’s where these sensations come from. And, yes, that’s often the case. Our sinuses can get so stuffy that the molecules responsible for producing a smell can’t reach the odour receptors embedded in our nasal tissue. When it comes to taste, we often lose tastebuds as we get older. They shrink, which diminishes our sense of taste. But this isn’t the case when we lose these senses to COVID-19.

The physiological chain of events responsible for our sense of smell and taste involves more than just taste and odour receptors. Those receptors send signals along nerves to the brain, and the brain must process the signals it receives any obstruction or dysfunction along that pathway from point of reception to point of perception, can impair the ability to smell or taste. When we lose our sense of smell or taste (or both) to COVID-19, the problem is in the brain.

Focusing diagnosis and treatment on the brain

Traditional treatments for anosmia, hyposmia, and ageusia target conditions that impact the sensory receptors, such as treating sinus allergies or nasal polyps to clear the sinuses. Other treatments, such as olfactory retraining, attempt to restore function to the nerves that carry signals from the sensory receptors to the brain. This retraining involves sniffing different scents daily to build and strengthen neural connections.

Approximately 10 percent of COVID-19 patients are considered long haulers, which means their symptoms last for several months after the infection is no longer active. This helps to explain why it can take so long for some patients to recover their sense of smell and taste.

One of our most recent patients with post-COVID inflammation complained of fatigue, memory lapses, and an impaired sense of taste. At 65 years old, she was concerned that this would be her “new normal.” After 30 days of treatment to reduce brain inflammation — with the use of peptides (including BPC-157), antioxidants, and vitamin C — she recovered completely.

How to regain your sense of smell naturally

The scents of so many things can bring joy. For some people, it may be the aroma of fresh cut grass or blooming flowers. For others, a newborn baby’s skin, or the scent of bread baking can bring feelings of calm and serenity. Smells can also warn of danger, letting us know there’s a fire, or food has gone bad.

Castor oil

Dr Sandra El Hajj, a naturopathic physician, recommends castor oil for anosmia. “Naturally, castor oil has been long used to restore smell loss, due to its active component, ricinoleic acid. Ricinoleic acid may help fight infections. It also helps reduce nasal passage swelling and inflammation caused by colds and allergies,” she says.

Castor oil comes from castor seeds. It is used as a nasya, or nasal passage treatment for restoring sense of smell by Ayurvedic practitioners.

Gently warm castor oil on the stove or microwave. Make sure it is warm and not hot. Place two drops of oil in each nostril twice a day: once upon waking and right before sleep.

Ginger

Ginger has a distinctive, pungent scent that makes it beneficial for use in smell training. You can use powdered or raw ginger for this purpose.

Dr. Hajj also recommends drinking ginger tea. “Naturopathically, drinking ginger tea tames down inflammation of the nasal airways, while reducing excess mucus formations that block nasal passages, causing loss of smell,” she says. To try ginger tea for anosmia, try using readymade ginger teabags.