As Tiffani Hutton recovered her sense of smell after COVID-19, she started to get whiffs of terrible odors.
Each time, she asked her husband, Cartell, if he smelled anything, but he didn’t. So, she checked expiration dates on their food, cleaned out the fridge and took out the garbage. She did it again and again.
But the smells grew worse. Soon, Hutton, 29, a consultant from Dallas, realized the smells were triggered by some of her favorite things: coffee; chocolate, fresh fruit, cucumber, roasted meat, all cooked vegetables, her bath soap, her 3-year-old daughter’s skin, her husband’s kiss.
They all smelled, she said, “like someone went fishing, put a fish on the counter and left it there for a month.”
The stench sometimes made her vomit. She stopped cooking for her family and eating with them. When Cartell ordered in chicken wings one night, she locked herself in her office upstairs and stuffed a towel under the door.
After a couple of weeks, Hutton typed: “Why does everything smell like rotting fish?” into Google and found a large community of people online suffering from the same condition. It’s called parosmia, a distorted sense of smell that can be triggered by colds and sinus infections, head injuries, chemical exposures or cancer treatments like chemotherapy and radiation.
A large surge of cases has followed the start of the COVID-19 pandemic. Barry Smith, founding director of the University of London’s Center for the Study of the Senses, said researchers have estimated that around 65% of those with COVID-19 lose their sense of smell. Among that group, the majority recover within a few weeks, but around one-fifth develop persistent problems, including parosmia. The condition, he said, causes profound distress.
“Your sense of smell is a very integral part of your self-awareness,” he said. “When it’s distorted, it leaves people feeling alien from themselves and their surroundings.”
Doctors, said Smith and others, have been caught off-guard by the surge of patients with parosmia. Hutton’s ear nose and throat doctor told her she was in “uncharted waters” and there was little he could do to help. The condition, which was previously rare, is poorly understood.
But small groups of researchers have started working with patients to unravel the mysteries of how the aroma of a fresh strawberry can travel through the nose and get misperceived as rotting garbage.
One of the online communities Hutton joined was the “Parosmia – Post COVID Support Group” on Facebook. There, members commiserate, share tips and celebrate signs of recovery.
The group was launched in December by Meagan Wiederstein of Schertz, Texas. Wiederstein, 36, had COVID-19 last summer, lost her sense of smell and got nearly all of it back before noticing that her favorite foods smelled rancid and sickly sweet.
Like Hutton, Weiderstein stopped being able to eat meat, dark chocolate, wine, coffee and all fried foods. She could, however, tolerate most vegetables. Thanksgiving, she said, was a nightmare as her family struggled to understand her sudden and extreme dietary restrictions.
“We’re all just supposed to eat, like, a vegetarian meal?” her husband asked. She tried to explain that she merely needed palatable options, including one or two sides that didn’t contain bacon.
“Until someone experiences parosmia, they will never understand it. Period,” she said.
Her support group counts nearly 10,000 members, and she receives 100 or more new requests to join each day, she said.
Wiederstein started to notice patterns in what people could and couldn’t eat. Coffee, meat, onions, and chocolate were almost universally reviled. Seafood, cinnamon, bubble gum and hot peppers, for some reason, were well tolerated. (Some users would add cinnamon to their coffee to disguise its newly off-putting smell). Steaming-hot foods were out, but room-temperature meals were OK.
The triggers for parosmia seemed utterly random.
Meanwhile, researchers started puzzling over these same patterns. Jane Parker, a flavor chemist at the University of Reading in England, wondered if the offending foods shared any common compounds.
Parker recruited volunteers with and without parosmia to sit in front of a machine that separates aromas into individual molecules. As the molecules emerged from the machine, volunteers sniffed them by placing their noses at the end of a tube projecting out from the device.
What she found surprised her. Individuals with parosmia reacted to two sets of compounds in coffee: those that contained either sulfur or nitrogen. People without parosmia described the compounds as “roasty” or “earthy.” But to those with parosmia, they smelled foul.
“For us, that was quite fascinating,” said Parker. “We now know that there’s a molecular basis for this horrible thing that parosmics are suffering from.”
As she looked further, she found that chocolate and roasted meats contained many of the same offending compounds as coffee. The common factor is the roasting process of coffee and cocoa beans, she said, and the aroma compounds derived when meat is browned.
Raw, boiled and steamed vegetables undergo little cooking compared to roasted or grilled meat, which could explain why Wiederstein and many other patients tolerate them. Parker and her colleagues posted their study online, but it has not yet been peer reviewed.
The new findings add to a growing understanding of what transpires in the nose and brain during parosmia. In a healthy person, aroma molecules pass through the nose and attach to olfactory nerves at the back of the nasal passages. Those nerves send signals to the brain which analyzes and interprets them as “coffee” or “barbecued ribs.”
Different molecules attach to and activate different nerves, like fingers striking piano keys, and that pattern is the one the brain responds to.
COVID-19, experts say, damages cells that support the work of olfactory nerves, causing the nerves to atrophy. From there, what happens is less clear, and scientists have many hypotheses.
Smith of the University of London said the fact that most patients recover their sense of smell before developing parosmia is telling. It underscores that parosmia is a sign of recovery. A leading theory has been that, as the nerves regenerate over a process of several months, they rewire themselves incorrectly and send the wrong signals to the brain.
“It’s as if you’re plugging them into the wrong port,” said Smith.
But then why would people with parosmia always smell terrible things? Why wouldn’t oranges smell like lavender and roses like freshly cut grass? That’s where Parker’s work comes in, Smith said.
Perhaps the first neurons to regenerate are the ones that pick up stronger odors, like sulfur, which is toxic in high concentrations. At that stage, many other neurons are still absent, so there’s nothing to mask or counterbalance that strong smell. The problem with that hypothesis, though, is that the bad smells that people with parosmia describe do not exist in real life. They seem to be novel smells created by the brain.
Stuart Firestein, a neuroscientist and olfaction researcher at Columbia University, compares parosmia with a condition experienced by people who have lost a limb. Some amputees continue to feel discomfort in their missing arm or leg, as if it is painfully twisted or broken.
“It seems that what’s going on is that when the brain doesn’t receive information that it’s expecting, it interprets that in a negative way,” said Firestein. “So if it’s a limb, it’s pain. If it’s olfaction, it’s a bad smell rather than a good smell.”
Parosmia, then, could be the brain’s way of sending a warning that it’s receiving incomplete data and there could be danger.
Because parosmia has not been well studied, there are no proven treatments for it. It does, however, fade with time in most cases — a process that can take a few months or more than a year.
On social media, people have spread misinformation about quick fixes. One is that burning an orange over an open flame, mixing it with brown sugar and eating it will restore one’s sense of smell. Another, advanced by a chiropractor, recommends flicking people with smell loss in the back of the head.
Neither will cure the disorder, said Chrissi Kelly, founder of AbScent, a British non-profit that supports people with smell disorders.
Many ENTs, including Dr. Tran Locke of Houston’s Baylor College of Medicine, recommend smell training — a form of physical therapy for the nose. It involves smelling essential oils several times a day in an effort to stimulate neurons to regenerate and better sync up with the brain.
Hutton has practiced smell training since seeing her ENT in Dallas and believes it is starting to help. Her kit includes eucalyptus, peppermint, tea tree, lavender, lemongrass and sweet orange scents.
Alongside treatments, people with parosmia have come up with numerous coping mechanisms. Hutton started a spreadsheet where she lists the foods she can tolerate. That makes it easier for her to combine them into meals and recipes.
A recent discovery that helped her is a company called Fody Foods that makes salsa, pasta sauce and other products without onions or garlic. Recently, she resumed drinking smoothies — which smell revolting to her because of the fresh fruit — by using a straw. “That works and doesn’t plague your sense of smell too much,” she said.
Jennifer Knight, a pediatric nurse practitioner from Fort Walton Beach, Fla., who works in a busy doctor’s office, drips essential oils into her facemask or sometimes wears a nose plug to block unwanted odors. She used to vomit in the bathroom whenever a colleague walked past her with a cup of coffee, she said.
Wiederstein has tried to push past her symptoms, challenging herself to eat foods she finds off-putting — something that many are unable to do without gagging. She’s resumed drinking wine, coffee and eating meat, though the flavors remain different and sometimes still have that “COVID smell,” a term many people use to describe the revolting odor.
Kelly of AbScent said patience is key when faced with parosmia. She suffered smell loss and parosmia in 2012 after developing a sinus infection. It took her more than two years to recover. Smell training, she said, is an important tool.
“It’s not a cure, but it’s a way of hastening your recovery,” she said. Kelly, who partners with Smith, Parker and other researchers on smell-related science, also urged patients to seek out mental health care for anxiety and depression.
That’s something Knight did. “You get so anxious, just not knowing where the next bad smell is going to come in,” she said.
The good news, said Smith of the University of London, is that about 90% of those with parosmia recover.
Kelly cautions that “recovery” is not the best word to use. She associates it with the rapid recuperation that follows infections like pneumonia or the flu. But parosmia is an injury to one’s olfactory system and follows the slower timeline of recoveries from car accidents and broken bones.
“You would not look in the mirror at a scar on your face and say, ‘When is the scar going to disappear?’” she said. “You would know that you had the scar and that’s something that happened to you. And that in time that scar would fade, and you would stop noticing it and go about your daily life. That has to be the way we look at it.”
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