When the fragrance of roses turns into the putrid smell of rotting fish, that’s Parosmia—an unsettling aftereffect of COVID-19.

In February, Mark Byrd from Atlanta realized that he, his wife, and young daughter had all contracted COVID-19. They each fell ill and lost their sense of smell, a telltale symptom of the virus.

Though Byrd had a rough case of COVID-19, it wasn’t severe enough to require hospitalization. His wife, who is immunocompromised, needed a monoclonal antibody infusion, but ultimately, all three recovered. His wife and daughter regained their sense of smell, but Byrd didn’t. "At the time, I didn’t think much of it," he recalls, assuming it would return eventually.

After four long months, Byrd's sense of smell finally started to return, but just faintly. Another month passed, and a strange, persistent metallic taste took over his mouth. That’s when things took a turn for the worse. While his smell came back, it was distorted. Hand soap now reeked of rotting flesh, roses smelled like excrement, and even a simple sip of beer made him gag. Strangely, no one else around him noticed these awful odors and tastes.

Desperate for answers and growing more suspicious that COVID-19 was the culprit, Byrd turned to the internet. He quickly discovered he wasn't alone—and certainly not crazy. While there was limited media coverage, thousands of people in Facebook groups had recovered from COVID-19 only to be left with this bizarre olfactory distortion. It had a name: parosmia.

What Is Parosmia and How's it Connected to COVID-19?

Parosmia is a condition that alters the way you perceive smells. In Byrd’s case, the odors were overwhelmingly unpleasant, like hand soap smelling like decaying bodies and the outdoors reeking of sewage. Ironically, Byrd was unable to detect foul smells that others could.

This peculiar distortion of smell is becoming increasingly common among those who have had COVID-19, lost their sense of smell (anosmia) and taste (ageusia), and recovered, but never fully regained their olfactory senses. Dr. Jennifer Grayson, director of otolaryngology research at the University of Alabama at Birmingham, explains that parosmia is not considered a long-term COVID symptom. Instead, it’s a complicating factor of the virus that could be permanent for some.

Parosmia is closely linked to phantosmia, a type of olfactory hallucination where people smell things that aren't actually there, like the scent of smoke when there’s no fire, according to Grayson. It can also be combined with dysgeusia, a condition that distorts taste. For instance, one member of a Parosmia/Post-COVID Facebook group shared that toothpaste tasted like "the smell of a landfill."

Other group members describe these strange smells and tastes as "dumpster juice," "hot garbage," "potting soil," "decaying flesh," and "dog," which can severely affect their quality of life.

Eating becomes an agonizing challenge for parosmia sufferers, as familiar foods that once tasted good now induce gagging or vomiting. (Try eating something that tastes like "rotting flesh.") Since parosmia can persist for months, many individuals end up losing weight, and some face depression or a deep sense of hopelessness, fearing they may never regain their sense of smell and taste.

How Common Is Parosmia?

Parosmia can be triggered by hundreds of different viruses, including something as simple as the common cold. Other factors such as head injuries, brain tumors, neurological conditions, medications, chemical exposure, and smoking can also lead to parosmia. However, the recent surge in cases tied to COVID-19 has drawn more attention to this disorder, according to Grayson.

A study published in the February 2021 edition of the journal Nature found that among COVID-19 patients who had lost their sense of smell, 56% developed parosmia about 2.5 months after losing their smell. For most, the symptoms persisted even six months later.

So, what causes parosmia in COVID-19 cases? Grayson explains there are three potential reasons. First, nasal congestion can cause swelling that blocks odor particles from reaching the olfactory nerves, but once the swelling subsides, smell may return.

Another cause could be viral damage to the tiny filaments of the olfactory nerves, or to the supporting cells around them. A third theory suggests that COVID-19 particles might trigger inflammation and cell death along the olfactory nerve all the way to the brain, damaging the olfactory cortex, the region responsible for identifying smells. "These cells must regenerate for smell to return," Grayson explains.

Treatment for COVID-related Parosmia

A lot of the research on smell loss recovery predates the COVID-19 pandemic and includes approaches like steroid nasal rinses and omega-3 supplements, which are relatively mild treatments, Grayson explains. However, the most promising option appears to be smell training.

An international panel of experts reviewed existing research and, given the surge in olfactory issues after COVID-19, they issued a consensus statement published in the journal Rhinitis, Sinusitis and Ocular Allergy. Their recommendation supports the use of smell training for treating post-COVID smell disorders.

Smell training revolves around four key scents — floral, fruity, spicy, and resinous. These are typically represented by scents like rose, lemon, clove, and eucalyptus, Grayson says. The training itself involves applying a few drops of essential oils for each scent on a cotton pad and inhaling deeply for 10 to 20 seconds, focusing intently on your memory of that particular smell. Grayson recommends practicing each scent a few times before moving on to the next, with breaks in between to let your nose rest.

"It’s crucial to stick with it every day, and don’t be discouraged if you can’t smell anything at first. That’s completely normal," Grayson adds. "It may take a while before you start detecting any scent." After following this routine for six months, most people see improvement in their sense of smell, according to a study published in The Laryngoscope in November 2020. The researchers believe the training helps the brain’s smell pathways regenerate and recover.

Is COVID-19 Parosmia Permanent?

It's still too early to determine whether COVID-19-related parosmia is permanent, Grayson explains. "Historically, prior to COVID, 85 to 90 percent of people would regain their sense of smell to a normal level within the first year of loss. But with COVID-19, the situation is much more uncertain. We don’t have clear answers yet."

The silver lining is that the return of any sense of smell — even if it’s unpleasant, like in Byrd’s case — is often a sign of recovery, Grayson says. "For individuals who lose their sense of smell entirely and don’t experience any parosmias, that’s a bigger concern. They may not regain their sense of smell at all."

A hopeful sign is that several members of the Parosmia/Post COVID Facebook group have shared their experiences of improvements in their sense of smell, with some even reporting a complete recovery from their smell distortions.

"I would urge people not to lose hope," Grayson advises. She encourages individuals like Byrd to begin and persist with smell training. Additionally, she suggests staying updated on the latest scientific research and maintaining contact with a local academic hospital. "As more studies emerge, additional treatments will likely be available," she adds.