- Over 27 million people worldwide have experienced COVID-related smell or taste loss.
- For many of these individuals, symptoms have persisted for over six months.
- New research suggests that most patients will regain these senses within two years.
- Research continues around exactly how COVID-19 impacts taste and smell.
- The loss of these senses was more prevalent with earlier variants of COVID-19, and fewer people are reporting these issues now that Omicron is the dominant strain of the virus.
When COVID-19 hit, several primary symptoms were brought to our attention — including a loss of taste and smell. And it soon became clear that, for some, this symptom was lasting long after the infection had passed.
Researchers have struggled to figure out how long it takes for these senses to return has been somewhat inconclusive. However, new research is now offering a more definite answer.
The research follows previous
At the two-year mark, 105 individuals (88.2% of the participant sample) who had experienced altered taste and smell at four weeks post-infection reported a complete resolution of symptoms. Meanwhile, 11 people (9.2%) noted a decrease in symptom severity, and three individuals (2.5%) reported no change or worsening of symptoms.
All patients in the study experienced the initial COVID-19 variant rather than the more recently emerged Omicron strain and subvariants. The loss of smell and taste appears to have been a symptom that was more common
Indeed, the study highlighted that the newer Omicron variant ‘has been observed to less frequently and less severely affect chemosensory function.’
The researchers noted that their findings of full sensory recovery in the majority of patients contradict some other reports. Furthermore, they stated, ‘patients should be reassured that recovery from smell or taste impairment may continue for many months after the onset.’
“The changes to smell and taste associated with COVID-19 infection and long COVID include complete loss of smell and/or taste, decreased smell and/or taste, and changes to smell and/or taste,” explained Dr. Vanessa Wu, at the University of California at Irvine (UCI) Health Post COVID-19 Recovery Service.
“The smell of burning is one I hear a lot from patients, [while] some say everything smells the same no matter what they are smelling,” revealed Dr. Amy Edwards, infectious disease specialist and assistant professor at the Case Western Reserve University School of Medicine in Cleveland, Ohio.
“I have a patient who tells me that any food that is warmed up tastes like chlorine, [and] a lot of people say meat can taste rotten, or like chemicals or metal,” Edwards continued. “It really can present in a variety of ways.”
Researchers have found
However, they found some men experience the symptoms more acutely during their onset.
“We don’t know why, on average, women take longer to recover their sense of taste and/or smell after a COVID-19 infection,” stated Wu. “One theory is [they] may have better baseline smell/taste, making them more sensitive to a change.” Other theories, she added, include the influence of estrogen and greater inflammation response.
Whether or not a person smokes and whether a person has both smell and taste loss (or just one of the two) have also been noted as
The researchers also point out it is not only impacting adults: olfactory loss and taste dysfunction are common COVID-19 symptoms among
As with many elements of the disease, uncertainty prevails — and “there are a few theories on how COVID-19 infection affects smell and taste,” Wu said.
Regarding smell, the primary thinking is that the infection impacts cells in the nasal lining. “Local inflammation occurs in response to the infection, which disrupts the ability of those cells to make and/or display smell receptors inside the nose,” revealed Wu. “The cells that support the health and function of olfactory (smell) nerve cells may also be impacted.”
Another hypothesis is that “the virus may directly affect the olfactory nerve cells, or that the inflammatory response impacts these nerve cells down the line,” continued Wu.
What about taste? COVID infection could be impacting taste buds directly, said Wu. “Researchers think the immune system’s inflammatory response to the infection can slow down how quickly taste buds renew and replenish.”
Finding your sense of smell or taste altered — or gone entirely — for an extended period can have marked effects on wider wellbeing.
First of all, there’s the obvious: enjoyment of food.
“Eating is a part of how we interact as humans,” said Edwards. “For a subset of the population, this pleasure has now been removed.”
Plus, reduced inclination to eat can negatively impact weight and nutrition.
Additionally, research has found that experiencing smell or taste loss ‘significantly reduces quality of life’, particularly with mental health. For example, one study of over 300 COVID patients with taste or smell loss saw 43 percent report feelings of depression, with another noting
There are also safety aspects to consider.
“Smell is one of the senses our body uses to look for danger, such as smelling smoke from a fire,” Wu stated, “so a persistent change in smell can potentially be a safety concern as well.”
Understandably, anyone experiencing a loss of taste or smell will look for approaches to prompt their return.
“I am not aware of any therapies for loss of taste,” stated Edwards — but smell-retraining therapy is a potential aid for noses.
“[This] involves regularly sniffing strong and memorable scents while concentrating on your memory of the smell,” explained Wu. “It is thought to stimulate the olfactory system and encourage/refine the connections in the brain that help interpret smells.”
Studies have also explored whether nasal or oral steroids could be beneficial in helping people regain their sense of smell, but findings are mixed and relatively limited, and more research is required.
Loss of smell and taste is a concern for many COVID-19 patients, and dysfunction can last for extended lengths of time. Yet, this new research indicates that most individuals could regain these fully within two years of infection.
However, it’s important to note that these findings only relate to those who experienced ‘mildly symptomatic’ COVID-19; researchers did not explore the impacts on patients with more severe symptoms.
For those experiencing smell loss or dysfunction, smell retraining therapy could help prompt the path to recovery. Meanwhile, scientists continue investigating other approaches that could aid in restoring these senses among COVID patients.