A group of olfactory experts are advising against the use of steroids to treat a lingering loss of smell caused by COVID-19. Instead, they suggest you try re-training your nose to sniff out certain scents.

It'll take time, possibly months, but if you try to get a whiff of at least four different aromas twice a day, it could help you recover faster and more fully, without any unwanted side effects.

The recommendation is based on a systematic evidence-based review, which concluded corticosteroids should not be the first treatment option for smell loss due to COVID-19.

These drugs are commonly prescribed to those with congested or inflamed noses, but this doesn't seem to be what's causing olfactory dysfunction in those with COVID-19, so it might not work.

Smell training, on the other hand, is a more evidence-based way to get your sniffer back up to snuff after a viral infection.

"As an expert group we strongly emphasize the initial consideration of smell training," writes the group.

"Smell training has no known side effects and is low cost. Moreover, it is the only available treatment… supported by a robust evidence base."

It's hard to compare steroids and smell training treatments for COVID-19 olfactory dysfunction specifically, as no controlled studies have been done.

That said, the idea of smell training has been around for a while. It's even been used with great success to help treat smell loss from other infections.

In 2020, for instance, a systematic comparison of potential treatments for post-viral smell loss - including olfactory training, systemic steroids, topical therapies, non‐steroidal oral medications, and acupuncture - found smell training should be the number one recommendation based on current evidence.

Today, we might need to implement this practice on a scale never before seen. Around 60 percent of those who contract COVID-19 experience a disturbance in smell, while about 10 percent have persistent symptoms lasting for weeks, even months.

Luckily, it seems most people do get better, and smell training might have something to do with that. At the start of 2021, a study of 1,363 coronavirus patients with olfactory dysfunction found 95 percent of patients recovered their sense of smell after six months.

These patients were advised to undertake two smell training sessions a day at home, although it was unclear how many people actually did this.

Corticosteroids have also been considered as a treatment option, but this medication isn't harmless. It can come with many unwanted side effects, including fluid retention, high blood pressure, and mood swings.

Plus, it might not even help. We just don't have enough evidence to say for sure. While some case reports suggest steroids may help people recover their lost sense of smell from COVID-19, without a control, it's unclear if these patients would have gotten better on their own - as, indeed, it seems many patients do.

Based on the current evidence, the authors join numerous other experts in calling for caution. Until randomized, placebo-controlled trials can be undertaken we should start with smell training, they say, and not steroids.

"[Smell training] has emerged as a cheap, simple and side-effect free treatment option for various causes of smell loss, including COVID-19," says Carl Philpott from the University of East Anglia in the UK.

"It aims to help recovery based on neuroplasticity - the brain's ability to reorganize itself to compensate for a change or injury."

This requires time, and not everyone is going to get better at the same rate. Older people, for instance, might take longer to get their sense of smell back as they have fewer olfactory receptor neurons.

Traditionally speaking, smell training relies on four odors: clove, rose, lemon and eucalyptus, but it really doesn't matter what you choose.

There might even be a benefit to focusing on familiar smells, like perfumes, lemon rinds, vanilla or ground coffee, and reflecting on memories while you sniff them. For the best results, you should change the four smells every 12 weeks.

If you're interested in learning more, Philpott suggests checking out the charity website Fifth Sense.

The study was published in the International Forum of Allergy & Rhinology.