To a COVID patient, coffee might smell like gasoline or feces
You’ve probably heard that a common symptom of COVID-19 is losing smell and taste.
“Eighty percent of patients who get COVID have some change in their smell or taste. For most of them, that change is pretty temporary,” said Dr. Sandeep Robert Datta, associate professor of neurobiology at Harvard Medical School.
Dr. Datta, who has been studying smell for the past 15 years, says researchers still don’t totally understand why COVID-19 causes anosmia, the medical term for the inability to smell and taste.
“It looks like cells in your nose temporarily get shut off like a light switch,” Datta explained. “After a couple weeks of healing, the light switch goes back on and your nose works again. In the patients that lose their sense of smell for longer, it looks like the neurons in your nose that detect odors, those cells might have been damaged by the virus. It takes a long time to rebuild those circuits and to heal that kind of extensive damage.”
A lot of people who suddenly lose their sense of smell and taste experience depression, anxiety, and isolation. Part of that is losing the joy that comes from tasting and enjoying food. But Dr. Datta says it’s also because smell is so closely linked to emotion; they’re physically located right next to each other in your brain. When you touch, see, or hear something, it has to travel a long way to get to the place in the brain that registers feelings, memory, and emotions.
“Smell is very different,” Datta said. “Smell is a super ancient sense. It’s like your sense of smell is hard wired for emotion and for memories, much more than the other senses. This explains why when we smell something that reminds us of our grandmother’s kitchen, we can be overwhelmed with emotion very quickly.”
He says smell is believed to be the very first sense to evolve.
“We’re very much used to thinking of smell as a kind of convenient accessory to our other senses. It’s the bonus sense, the one we don’t really need. It’s not as important as hearing or vision or touch. But it turns out, we depend on our everyday experiences with smells to maintain our sense of emotional well-being,” he said. “As we navigate our environments, we know those environments are familiar to us and safe, in part because we’re smelling familiar odors. It turns out that’s very important to our overall sense of well-being. It’s well-known clinically that people who suddenly lose their sense of smell can be at risk of neuropsychiatric disorders, like depression.”
Dr. Datta says a lot of COVID-19 patients have reported experiencing something called parosmia as well.
“Parosmias are when you smell something and it actually smells different than it’s supposed to,” he explained. “People with parosmia sniff coffee and instead of smelling delicious, it smells like gasoline. That will obviously put you off of food. For those patients in particular, it’s a real challenge to find foods that they can tolerate given that everything suddenly smells like turpentine or feces.”
“We don’t actually know why parosmia tends to be bad. Wouldn’t it be amazing if everything suddenly smelled like flowers and candy?,” he laughed.
One theory for parosmia is that losing your sense of smell makes you vulnerable to danger, perhaps from fire or poisons that you wouldn’t be able to detect, so your nose overcompensates by making everything smell like something you should avoid.
Of course, if you can’t smell, you won’t taste much either. Dr. Datta says flavor is sensed from both taste on the tongue and smell in two ways: You detect flavors by breathing in through your nose, but also there’s scent that travels up the back of your throat and into your nasal cavity while you’re chewing.
When people suddenly lose their sense of taste, they might react in two ways: Either they overeat because flavorless food isn’t satisfying, or they become so defeated by the loss of taste, they don’t eat enough and lose weight. One solution is to eat food with lots of texture and crunch, and play with contrasting temperatures, which can still be detected.
“When I was younger, I lost my sense of smell,” said Dr. Datta, who experienced this long before he became a doctor. “I had some chemotherapy and afterward, I couldn’t smell at all. I gravitated toward a food that had a ton of texture: bacon, egg, and cheese sandwiches with tons of hot sauce.”
“It turns out that the way we detect hot sauce is different from smell and taste,” he said. “There’s basically another sense that no one talks about, a secret sense called chemesthesis where a whole different set of cells and neurons are responsible for detecting things like spicy and cool. The normal cells in your nose are responsible for detecting smells, and the cells on your tongue are responsible for salt, or bitter, or sweet. But there’s actually a whole separate chemosensory system devoted to the cooling scents of menthol, or the spicy sense of peppers. And so I’d just load up on the hot sauce on these sandwiches.”
A sixth taste! Now that we’ve all become accustomed to the fifth taste, umami, scientists have decided to throw another new one our way.
This was an excerpt from Rachel Belle’s newest “Your Last Meal” podcast episode with Ben & Jerry. Click here to listen, listen where ever you get podcasts (Apple, Spotify, Stitcher), or text BEN to 98973 and we’ll send it to you.
- Tune in to KIRO Radio on weekdays to hear Rachel Belle.
- Rachel Belle hosts the James Beard Award nominated podcast Your Last Meal and she's an Edward R Murrow award winning feature reporter. Follow Rachel on Instagram.