A city council committee is expected to decide Monday whether to allow a North York man to chop down a backyard walnut tree on the grounds that his family members are allergic to the nuts.

But staff, some city councillors and allergy experts have expressed concern that granting the man permission could lead to an avalanche of similar claims, and ultimately the destruction of thousands of healthy nut-bearing trees.

"We can't rid the world of walnut trees," said Jennifer Gerdts, executive director of Food Allergies Canada. "We need to practise avoidance strategies."

Although walnuts can trigger serious allergic reactions, she said someone would actually have to eat the nut — an unlikely scenario.

That's an opinion that's backed up by the city's medical officer of health. In a report to North York community council in June, staff concluded that there is "no evidence to suggest that black walnut-bearing trees pose a significant risk to those with allergies."

Jennifer Gerdts, executive director of Food Allergy Canada, says allergies to black walnuts can be managed without cutting down the trees. (Food Allergy Canada)

Even so, councillors asked for a report from the city solicitor earlier this year. They want to know what legal repercussions the city could face should a resident become ill after exposure to a black walnut tree.

That report was delivered to North York councillors last week, but it's being kept secret.

North York community council, which has the authority to grant or deny the homeowner's application without the approval of city council, is expected to make a decision at its Monday morning meeting.

CBC Toronto has asked the homeowner for an interview. So far, those calls have not been returned.

Deputy Mayor Denzil Minnan-Wong, who represents Ward 16 where the homeowner lives, said he's worried that if one homeowner is granted permission to cut a tree down because of a potential allergic reaction, it could be the start of many more applications to remove black walnut trees.

"When I satisfied myself that there weren't any young children involved, I was satisfied that there is not really a significant amount of risk," he said. "And the urban canopy does need to be protected."

Deputy Mayor Denzil Minnan-Wong says allowing the black walnut trees to be taken down could force the city to allow hundreds of other homeowners to get rid of healthy trees. (Mike Smee/CBC News)

City staff go even further in a January report, saying forestry officials express concern that allowing the destruction of this walnut tree because its fruit could trigger an allergic reaction could lead to the loss of thousands of other trees — not just black walnuts.

"If the City accepts that the nuisance and risk factors of these trees outweighs their environmental and health values, this could lead to the potential removal of hundreds of street trees and thousands of park and private walnut trees in Toronto," staff wrote.

"Additionally, there are thousands of other nut-bearing trees across the city which could also be the subject of similar concerns."

For years, homeowners have been applying for permits to remove healthy black walnut trees because they excrete a chemical that tends to overwhelm all other nearby plants, ruining gardens. As well, their large nuts can damage property.

Those arguments have fallen on deaf ears at city hall, though.

Forestry officials have said the importance of growing the city's tree canopy far outweighs any nuisance caused by falling or allergy-inducing nuts.