Michele Miller, of Bayside, N.Y., was infected with the coronavirus in March and hasnt smelled anything since then. Recently, her husband and daughter rushed her out of their house, saying the kitchen was filling with gas.

She had no idea. Its one thing not to smell and taste, but this is survival, Ms. Miller said.

Humans constantly scan their environments for smells that signal changes and potential harms, though the process is not always conscious, said Dr. Dalton, of the Monell Chemical Senses Center.

Smell alerts the brain to the mundane, like dirty clothes, and the risky, like spoiled food. Without this form of detection, people get anxious about things, Dr. Dalton said.

Even worse, some Covid-19 survivors are tormented by phantom odors that are unpleasant and often noxious, like the smells of burning plastic, ammonia or feces, a distortion called parosmia.

Eric Reynolds, a 51-year-old probation officer in Santa Maria, Calif., lost his sense of smell when he contracted Covid-19 in April. Now, he said, he often perceives foul odors that he knows dont exist. Diet drinks taste like dirt; soap and laundry detergent smell like stagnant water or ammonia.

I cant do dishes, it makes me gag, Mr. Reynolds said. Hes also haunted by phantom smells of corn chips and a scent he calls old lady perfume smell.

Its not unusual for patients like him to develop food aversions related to their distorted perceptions, said Dr. Evan R. Reiter, medical director of the smell and taste center at Virginia Commonwealth University, who has been tracking the recovery of some 2,000 Covid-19 patients who lost their sense of smell.

More here:
Some Covid Survivors Haunted by Loss of Smell and Taste - The New York Times