With the number of Lyme disease cases increasing each year, a pressing question looms: are Canadian outdoorspeople being shortchanged by not having access to permethrin as a protective tool?
Permethrin is a synthetic insecticide modeled after pyrethrins, which are naturally derived from chrysanthemum flowers. It targets the nervous system of ticks that come into contact with treated fabric, causing paralysis and eventual death.
Permethrin spray has been approved in the US for tick-repellent use on clothing for more than 30 years. Since 2003, clothing pre-treated with permethrin has also been available and widely used, remaining effective through dozens of washes. Research suggests that the chemical binds well to fabric and is not easily dislodged.
“Permethrin is one of several options for tick-bite prevention and while it would definitely be helpful to have it approved in Canada, it is also important to be aware of its proper use and its potential for harm to animals and small children,” said Dr. Sarah Keating, a board member of CanLyme — a national, volunteer-based organization dedicated to promoting research, education, diagnosis, and treatment for Lyme disease and related illnesses.
In Canada, permethrin is already used in lice treatments, pet and livestock products, and various pesticides. However, only one product — Mark’s No Fly Zone pre-treated clothing — has been approved for human use in tick prevention. That approval process took 12 years, and notably, the clothing is not available in camouflage. In the US, testing of permethrin-treated clothing even included assessments of children mouthing the fabric, which was deemed safe. However, the Environmental Protection Agency also raised concerns that permethrin could be carcinogenic if ingested.
To be approved for use in Canada, any chemical must be registered through the Pest Management Regulatory Agency (PMRA), which requires the manufacturer to submit comprehensive scientific data to evaluate potential risks to human health and the environment. While Health Canada states that new approvals can take up to two years, this contradicts the 12-year timeline reported by Mark’s.
When asked why Canadian approval is so rigorous even for products already assessed in the US, Health Canada spokesperson Anna Maddison said the PMRA monitors the status of chemicals in other countries and jurisdictions but has to conduct its own assessment.
“All pesticides used in Canada must meet the Pest Control Products Act requirements and its regulations,” she said. “Before a pesticide is registered for use or sale in Canada, it must undergo a rigorous scientific assessment process that provides reasonable certainty that no harm to human health and the environment will occur when pesticides are used according to label directions.”
As seen during the COVID-19 pandemic, emergency approvals are possible. With Lyme disease cases increasing from 144 in 2009 to 2,544 in 2023, some advocates are asking whether a similar urgency should apply. Although those numbers remain below the threshold for epidemic status, emergency registration could be pursued if sponsored by a relevant provincial or federal agency.
Keating noted that some within the Public Health Agency of Canada have acknowledged that reported Lyme case umbers may need to be multiplied by 13 to reflect reality more accurately.
She believes declaring Lyme disease an epidemic would help galvanize action.
“Too many Canadians are suffering needlessly from a disease that deserves further study and better approaches to diagnosis and treatment,” Keating said.
The path to wider permethrin approval in Canada remains unclear. PMRA would not confirm what applications are currently under review but pointed to its online database, which lists a few potential new products containing permethrin — though no further details are available.
Originally published in the June-July 2025 issue of Ontario OUT of DOORS
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