Researchers in the UK say people who have lost their sense of smell due to covid-19 are better off using “smell training” at home, rather than steroids, to help get their sniffer back in working order.
The loss of smell, also known as anosmia, is one of the more common complications of covid-19, especially for those with mild acute infections. Most people’s covid-related anosmia does go away after a short while, often without any help. But some people are at risk of losing at least some degree of smell long-term. It’s thought that early treatment can help prevent permanent anosmia, but there are no clear standards for what might work best.
The researchers behind the current study, published in the International Forum of Allergy & Rhinology, looked at the medical evidence collected so far for treating covid-related anosmia. They found that, for people who are worried about forever losing their sense of smell after covid-19, the simple home remedy of smell training is likely a better first option than steroids.
Viral infections can damage the connections leading up to the brain that are responsible for processing smell, mainly the olfactory nerves. Over time, these nerves can be repaired or rewired to restore their function. Smell training is supposed to work by speeding up this process — a sort of physical therapy for the olfactory nerves.
There are slightly different variations to smell training, but the basic exercise asks sufferers to collect four strong, distinctive smells and sniff them for a brief period once or twice a day. These scents can be anything noticeable enough, but emotionally significant or pleasant smells may be more effective. The smells used in the original research on smell training (known as the Hummel method) were rose, eucalyptus, lemon, and clove. Benefits are most noticed in people who practice smell training for around four to six months.
Smell training “has emerged as a cheap, simple and side-effect free treatment option for various causes of smell loss, including covid-19,” study author Carl Philpott, a smell and taste researcher at the University of East Anglia, said in a statement released by the university this week.
Corticosteroids are one of the few drugs known to lower the odds of death and worsening illness from severe covid-19, and they work by reducing inflammation. Some doctors have wondered if they could help with covid-related anosmia as well. But when the researchers went digging through the literature, they couldn’t spot a clear benefit from their use, based on research involving covid-19 and other viral infections known to cause anosmia.
“What we found [is] that there is very little evidence that corticosteroids will help with smell loss,” Philpott said. “And because they have well known potential adverse side effects, our advice is that they should not be prescribed as a treatment for post-viral smell loss.”
Steroids could still be studied as a treatment for covid-related anosmia, but if so, only in the context of rigorous clinical trials, Philpott and his colleagues argue. And they may be more effective at treating non-viral causes of anosmia that are related to inflammation, such as chronic sinusitis.
Either way, most sufferers recover even without seeking treatment for their busted odor detector. “Luckily most people who experience smell loss as a result of Covid-19 will regain their sense of smell spontaneously,” Philpott said. “Research shows that 90% of people will have fully recovered their sense of smell after six months.”