Post-COVID smell problems? Ontario researchers investigate treatments

Despite the impact post-COVID parosmia has on people's lives, with half of respondents reporting depression, researchers say not enough is known about it.

Researchers at Western University are focusing on what they say is an understudied issue that has a major impact on quality of life: parosmia.

The disorder involves the distortion of smell, so scents that people once found pleasant – like coffee, chocolate or perfume – end up smelling disgusting to them. According to a survey led by researchers at Western University, more than half the respondents reported that parosmia has resulted in depression.

Issues with smell, or olfactory dysfunction, are common during and after COVID-19 infection, impacting between one- and two-thirds of symptomatic patients according to previous studies, the survey authors say. It’s estimated that eight to 32 per cent of people who experience issues with smell following COVID-19 infection are impacted by parosmia, which specifically involves the distortion of smell.

Despite its prevalence, researchers say literature on it is “scarce” and it is unclear how the disorder develops in the first place.

Of the survey participants, only three per cent reported full recovery from post-COVID-19 parosmia, with a mean recovery time of over 14 months.

While the most commonly used treatment was smell training (74 per cent), the most successful treatment reported in the survey was stellate ganglion block, or SGB.

Only 16 per cent of respondents were treated with SGB but 45 per cent of them reported improvement, compared with only 10 per cent who reported improvement with smell training.

SGB involves injecting a local anesthetic into a collection of nerves in the neck.