Skip to content

Sniff test: How peanut butter could help identify COVID-19 carriers

Dana Small, 48, a Victoria-born psychologist and neuroscientist who teaches both psychology and psychiatry at Yale University, is developing a peanut-butter sniff test for research into detecting loss of smell in otherwise asymptomatic carriers of COVID-19. Photograph By PIETER VAN DOKKUM

VICTORIA, B.C. — Peanut butter and jam make for a great sandwich pairing, but they’re also key ingredients in some novel research — a sniff test to identify otherwise asymptomatic COVID-19 carriers.

Dana Small, 48, a Victoria-born psychologist and neuroscientist who teaches psychology and psychiatry at Yale University, says if loss of smell is an early symptom of COVID-19, a test using simple ingredients found at home could lead to early detection.

“Identifying asymptomatic carriers is absolutely critical in stopping the progression of the pandemic, I believe,” Small said. “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.”

The idea stemmed from a conversation in March with two of Small’s friends: Rachel Herz, a Canadian adjunct professor in psychiatry and human behaviour at Brown University in Rhode Island, and Theresa White, a sensory psychology expert at Le Moyne College in New York.

The three were enjoying Saturday afternoon cocktails via Zoom when the discussion shifted to COVID-19 symptoms, including reports of a loss of smell or taste.

The next day, Small read about people in London, England, showing up at ear, nose and throat clinics because of a loss of smell, only to later test positive for COVID-19. “That’s when the lightbulb went off,” Small said.

Typical symptoms of the virus include fever, fatigue, cough and difficulty breathing, but initial loss of smell is one of a number of other symptoms that have been reported, including abdominal pain and nausea.

Given the prolific transmission of the deadly virus, which has infected more than 2.5 million people around the world, early detection in people with no classic symptoms is important.

Provincial health officer Dr. Bonnie Henry has said that the literature on COVID-19 suggests asymptomatic spread is not a major driver and the vast majority of transmission happens when people know they are sick, although she noted this week “the jury is still out.”

But Small said even if it’s just a small number of people, those who are asymptomatic but have smell loss could be flagged and prioritized for testing, or at least have the option to self-isolate.

“A single person who doesn’t know they are carrying the disease and infecting people can infect a ton of people,” she said. “So the real key then to stopping the spread of the disease is to identify those people.”

The smell test could also be used for at-home or at-business screening, she said.

To make a test that is readily available, safe and affordable, Small thought about everyday pantry items: peanut or nut butters, jam or jelly. (Peanut butter has also been used to detect the loss of smell in Alzheimer’s patients.)

These items — called pure odorants — stimulate olfactory senses without triggering the trigeminal nerve, which irritates or tickles the nasal passage.

As a control measure, a complementary test — sniffing vinegar, rubbing alcohol or coffee, for instance — would trigger irritation in the nasal passages.

If over the duration of testing, the pure scent of the peanut butter fades, but the vinegar continues to trigger the nasal passages, it’s a likely sign that someone’s sense of smell is deteriorating.

Sense of smell can deteriorate slowly without a person readily noticing.

The at-home olfactory test will likely be done through a website and involve a brief survey of about four questions asking respondents to rate their general ability to detect scents, note any change in the ability to smell, rate the intensity of the smell of the peanut butter, and finally rate the intensity of the vinegar.

The data collected will be de-identified and over time would build up information that could be fed back into the survey.

Small is hoping for about $50,000 in funding — through her not-for-profit Modern Diet and Physiology Research Labratory — to hire at least a part-time data analyst and pay for other business and legal costs. A Montreal web designer has already contacted her and offered to donate the creation of a website.

The site could be up and running in a couple of weeks and widely available, she said.

A much larger second research study has already been approved, though it’s also not yet funded, through Yale University.

In the second initiative, researchers want to survey about 3,000 health-care workers — everyone from physicians to nurses and orderlies — in the Yale University Hospital system. More than 20,000 people in Connecticut have tested positive for COVID-19.

“Right now, New Haven is peaking and this is the chance to get big numbers,” Small said. “That’s the urgency.”

The health-care workers at moderate to high risk for infection and transmission are already being tested for COVID-19 every three days. Yale researchers want them to sign up to take the same peanut-butter-and-vinegar-type survey test.

“We can use the smell ratings to see if we can predict who becomes positive,” Small said. “This will be able to answer the question: Is smell useful in determining asymptomatic carriers?”

By tracing health care workers’ sense of smell while testing for COVID-19, Small said, researchers could determine if smell loss is coincident with a positive COVID-19 diagnosis.

“By tracking those ratings over days and also the person’s subjective experience, we can learn if smell loss association with COVID-19 is gradual and occurs before people really notice, or if it comes on all of a sudden, and most importantly … can smell loss be used prospectively to identify asymptomatic carriers — that’s really the key question. That’s the research we’re doing at Yale.”

The research will cost in the ballpark of $450,000, including researchers and analysts, and take up to 18 months. In a best-case scenario, a vaccine is found first, “but nobody knows,” Small said. The research could also “keep us from being so flat-footed” when the next respiratory virus comes along, she said.

A grant request has been submitted to the U.S. National Institutes of Health, but even if it’s approved, the money wouldn’t come until the fall.

“We really need to get into the hospital and do these tests like, yesterday,” Small said.

If smell loss is determined to be a symptom, then a large-scale olfactory test can be developed to identify some portion of asymptomatic carriers, she said.

The outpouring from people who want to help, especially from fellow Canadians, has been “heartwarming,” Small said.

“So far, we don’t have anything in the bank, but Yale is talking to a number of people. Even small donations toward this research will get us started.”

Psychologically, the social isolation of the pandemic is very difficult, partly because people feel like they don’t have control over their situation, she said.

“Now, doing a smell test doesn’t actually give me much control, but at least it’s something. It felt good to be able to do this, to be able to participate, at least in some way.”

[email protected]

Read more from the

push icon
Be the first to read breaking stories. Enable push notifications on your device. Disable anytime.
No thanks