COVID-related smell loss may last years

A scratch-and-sniff test revealed people’s ability to detect scents two years after infection

A man sniffs a cup of coffee while holding a spoon.

After COVID-19, some people may experience smell loss, a symptom that may persist for years.

John Coletti/Getty Images

Maybe you can’t detect the scent of grass anymore. Or maybe coffee’s aroma now triggers disgust. After getting COVID-19, your sense of smell may seem persistently off. You’re not alone.

Even years after an infection, most people who say they have smell loss do indeed have a dulled sense of smell when formally tested, scientists report September 25 in JAMA Network Open. And people who thought they were smelling just fine often had problems, too, says Leora Horwitz, a general internist at NYU Langone Health. “Sometimes people don’t even recognize it when they have smell loss,” she says.

Her team’s work, part of the National Institutes of Health’s RECOVER Initiative to better understand the lingering effects of long COVID, is the first large-scale study to measure COVID-related smell deficits. It’s common for people to report the symptom, but very rarely do scientists actually test it, Horwitz says. That makes it difficult to understand, “How bad is it? How long does last? What kinds of smells do people lose?” she says.

Horwitz’s team answered some of those questions by giving a scratch-and-sniff test to more than 3,000 study participants. People tried to identify 40 different scents, like turpentine, bubble gum and lemon, selecting a multiple-choice answer for each. An average of two years after an infection, 80 percent of people who reported having an altered sense of smell had trouble detecting scents on the test, the team found. On average, these participants scored in the 16th percentile for their age and sex. “That was pretty bad,” Horwitz says.

Having a subpar sniffer might not sound like a big deal, but it can carry consequences. You might not be able to smell a gas leak, spoiled food or smoke from a fire, Horwitz says. Getting diagnosed is also important so people can consider seeking treatment. Though treatments to restore smell loss — like retraining the nose to detect scents — are still in development, they may work better if done early.

For Horwitz, many questions about COVID-related smell loss remain. The researchers don’t know if it’s linked to later cognitive challenges, for example. (Smell loss can be an early symptom of Parkinson’s disease and other neurodegenerative disorders.) The team hopes to continue performing smell tests on study participants to follow the trajectory of their recovery. We “still don’t really understand how long this smell loss will last,” she says.

Meghan Rosen is a senior writer who reports on the life sciences for Science News. She earned a Ph.D. in biochemistry and molecular biology with an emphasis in biotechnology from the University of California, Davis, and later graduated from the science communication program at UC Santa Cruz.