Imagine something pleasant smelling rotten or like poop.

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Loss of sense of smell is a well-established symptom of COVID-19, so much so that it can be used to diagnose the illness. While most people who suffer from smell loss due to COVID recover it quickly (within four weeks for 89% of people, per a July 2020 study), the remaining 11% report ongoing smell loss or something equally troubling: smell distortion, which is medically known as parosmia.

"While anosmia is a complete loss of smell and hyposmia is a decreased sense of smell, parosmia is an alteration of the sense of smell," Seth Lieberman, MD, assistant professor in the department of otolaryngology at NYU Langone Health, tells Health.

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How does parosmia change your sense of smell?

The smell distortion is not a change for the better. People with parosmia say that everything smells unpleasant, even rotten or disgusting. "A piece of fruit may smell like chemicals, or even worse, like fecal matter," Dr. Lieberman says.

Carol Pitz, from Chanhassen, Minnesota, told Smithsonian Magazine that she experienced parosmia for the first time in August 2020, months after testing positive for COVID-19. "It's a unique smell," she said. "I don't even know what it is. It's like a combination of burnt toast, and something just icky enough to make me sick to my stomach."

Another parosmia sufferer is 11-year-old Lorelai from North Carolina, whose mom Danielle Meskunas spoke to local TV station WNCT last week. Meskunas said Lorelai had COVID-19 back in November and lost her sense of taste and smell. She'd started to regain her ability to smell by late January, but a couple of weeks later something strange happened.

"She could smell a little bit, but things didn't smell like she thought they should," Meskunas said. "She was basically saying things smelled like rotten food, like something that had been sitting in the fridge."

Anybody with COVID-19 can get parosmia

Parosmia is affecting a growing number of people with COVID-19. It's not a symptom of the early stage of the illness; it appears to be a—very unpleasant—side effect.

Parosmia seems to arise in only some of those suffering COVID-19-related anosmia and "occurs later on in the course of the disease or during recovery," Charles Bailey, MD, medical director for infection prevention at Providence Mission Hospital and Providence St. Joseph Hospital in Orange County, California, tells Health. "It is believed to be due to an impact of the infection on the olfactory nerves' ability to interpret odors and aromas, and it can be seen in the aftermath of other types of viral infections."

So far, there's not a huge amount of research on parosmia in COVID-19 patients. But an international study of people with recent smell loss, published in Chemical Senses in June 2020, found that 7% of more than 4,000 respondents reported experiencing parosmia.

While most people recover within two to four weeks, a considerable percentage (estimated at around 10%) develop long-term olfactory dysfunction lasting for several months—and it's permanent for some people, Dr. Lieberman says. "The long-term data is lacking, so we do not know the prevalence of permanent dysfunction yet," he adds.

Can parosmia be treated?

Recovery of sense of smell seems to depend to some extent on nerve regrowth, Dr. Bailey says. That means there may be little that can be done to accelerate the process.

"There's no significant data at this point on any treatments for COVID-19 specific olfactory loss," Dr. Liberman says. The only level 1 evidence (meaning a randomized controlled trial) that has shown an effective treatment is something called olfactory training, he says.

This exposes the nose to a variety of odors and aromas, typically rose, lemon, cloves, and eucalyptus. According to Dr. Lieberman, patients sniff each odorant twice a day for about 15 seconds, for a period of three to six months.

Often, intranasal corticosteroids are also recommended, and a range of other treaments, such as omega-3 supplements and oral steroids, may be prescribed—but Dr. Lieberman says there's not good evidence for their effectiveness.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDCWHO, and their local public health department as resources.

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