“Identifying asymptomatic carriers is absolutely critical in stopping the progression of the pandemic, I believe,” Professor Small says. “So if there is odour loss with some — even if it’s only a small percentage of people — identifying them as carriers would be significant.”
Losing one’s sense of smell isn’t like losing one’s car keys. When the keys go missing, you recognize the loss in an instant. But a person’s sense of smell can slip away quietly, over a period of time, without the person noticing it is going, going, going, until it is effectively gone.
Small and her pals agreed that a simple do-it-at-home sniff test, using common household items, would allow participants — the great mass of us — to start tracking their sense of smell. In this way, an asymptomatic carrier who feels like a million bucks, but notes a diminishing sense of smell one day to the next, could consider quarantining, ASAP, instead of carrying on until their olfactory sense disappears altogether.
Hence, says Small, the birth of the peanut butter sniff test. Peanut butter, so good on toast, and always a friend to jam, is a North American staple that stimulates the olfactory sense exclusively, unlike, say, ground coffee — a treat to inhale, no doubt — but a fragrance that fires both our sense of smell and the trigeminal nerve governing sensations like “pain and tickle,” which influence how one registers an odour.
As a control on the peanut butter, sniff-test participants are asked to breathe in a snout full of vinegar, another household staple, like coffee, that fires the trigeminal nerve. The big idea? If a subject is registering the vinegar, but the scent of the peanut butter is fading away, they can be confident their sense of smell is decreasing.
“If we find there is a trajectory of diminishing smell over days, we would be able to identify asymptomatic carriers, even before they were conscious of losing their smell,” says Small. “And in those, let’s say, five days, there could otherwise be lots of transmissions.”
And what if you have a peanut butter allergy? Ouch!
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