For many who are infected with the coronavirus, loss of smell is a symptom that makes its presence known early on. While in most cases, the sense of smell and taste eventually recovers, many survivors who now live with what is known as “long COVID” are also experiencing parosmia — a smell dysfunction where natural odour is usually transformed into an unpleasant aroma.
“About 60% of people acutely affected by COVID-19 will get smell loss; of those that get smell loss, about 10% get persistent symptoms that last for more than four weeks,” said Carl Philpott, professor of Rhinology and Olfactology, Norwich Medical School. The issues associated with this can range from loss of perception of flavour, poor quality of life to not being able to detect hazards like gas leaks, he said.
Along with researchers from across Europe, Philpott and his team published a study last month revealing that smell recovery is possible through the process of smell training. This involves sniffing at least four different odours twice a day every day for several months. It is recommended that the training take place for at least six months. The participants received a variety of smell training kits consisting of different odours, including eucalyptus, clove, lemon and rose.
“The process of doing [smell training] really stimulates the smell pathways and encourages regeneration.”
The research was undertaken before the spread of COVID-19 and the subjects largely had smell dysfunction as a result of viral infections. “The process of doing [smell training] really stimulates the smell pathways and encourages regeneration,” Philpott told Re:Set. Smell pathways, he explained, unlike hearing and sight have plasticity, so they can get better or worse. Neuroplasticity is the brain’s ability to reorganize itself to compensate for injury or adjust to a change.
“You see this if you do brain imaging studies, you can see that the nerve pathways actually get bigger if you train and improve things,” Philpott said. According to him, it is an effective rehabilitation technique and helps people get recovery of not necessarily all, but some smell functions.
Because of the simplicity of the technique, Philpott reiterated that it can be done using easily available elements like aromatherapy oils or smelling kits without the supervision of a doctor. But, the patient should have been familiar with the smells prior to losing or experiencing a change in their sense.
“The more recent studies done in the last five years have shown that if you change the smells every three months and do that for a longer period of time,” Philpott said, “the results from that are better than just training with the same four smells.”
The promising outcomes that smell training has shown in patients recovering from viral infection-related smell loss point researchers to believe that it could be useful for those recovering from COVID-19 related smell loss.
There is an ongoing study in the U.K. that is exploring smell training in patients who’ve specifically had COVID-related smell loss, noted Philpott. “When that’s completed, we’ll have more data on that.”