Doctors are developing therapy to restore lost sense of smell in Covid patients

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For most people, the loss of smell that comes with a cold or allergies is familiar. It’s also one of the most common symptoms of Covid-19—and, for some, one of the longest-lasting. As we emerge from the pandemic and doctors grapple with how to help Covid long-haulers, olfactory retraining is becoming a hot topic. In March, KU’s medical system opened the area’s first long-hauler clinic to deal with lingering brain fog, fatigue, shortness of breath and the loss of smell and taste. Olfactory training—like physical therapy, but for your sense of smell—is among the offerings. Here are five things you should know about it.

It’s a new field. Olfactory training was pioneered by German psychologist Thomas Hummel. Back in 2009, Hummel published a study in which he directed patients to smell four essential oils (rose, lemon, clove and eucalyptus) and try to identify them. This training was done twice daily for twelve weeks. Hummel’s technique was effective, so when Covid patients started reporting loss of smell, other doctors looked to Hummel.

Doctors are treating your brain, not your nose. As far as doctors can tell, the loss of smell after Covid is caused by the brain and associated neurons not firing the same way they did before infection. Doctors are trying to retrain them and rebuild the pathways, says Dr. Jennifer Villwock, an otolaryngologist (commonly known as an ENT) at KU. The treatment regime involves “consciously recalling the scent” as a patient inhales because “linking these things together should strengthen their connection.”

Consistency is key. At KU hospitals, Villwock has patients consciously recall the scent they are smelling before and while they smell it. Like physical rehabilitation, it’s all about repetition. “The more training sessions completed, the better the results,” Villwock says. “This is a true training regimen, just like going to the gym.”

The stronger the smell, the better. The most effective treatment does not involve getting a patient to try and pick up on a faint whiff of an obscure scent. Rather, studies show that strong scents smelled consistently work the best. Anyone working to restore loss of smell at home should ask for help picking strong, common scents. “If you have no sense of smell and are training on essential oils or household products at home, I would recommend confirming with someone in your life that what you are training on is a strong odor that is representative of that scent,” Villwock says.

Other options are limited. Because the field is so new and has been understudied, there are no other treatments that have been subjected to randomized, placebo-controlled studies, Villwock says. Among the other treatments being looked at are oral supplements like zinc, alpha lipoic acid and omega-3s.  Doctors are also looking at topical steroids to decrease nasal inflammation and topical theophylline, which relaxes and opens air passages. “With larger trials, this may become an option in the future,” Villwock says.

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