The short answer
Permethrin-treated clothing plus DEET on exposed skin. The U.S. military has factory-treated uniforms with permethrin since 1993. The Canadian Armed Forces use a similar system.
The DOD Insect Repellent System
The U.S. military calls it the DOD Insect Repellent System, and it’s a layered approach:
Layer one: permethrin-treated clothing. Every Army Combat Uniform and Marine Corps Combat Utility Uniform is treated with permethrin using special binders so it lasts the lifetime of the garment. Permethrin doesn’t repel ticks. It kills them. A tick crawling across treated fabric receives a lethal dose.
Layer two: DEET, picaridin, or IR3535 on exposed skin. Since permethrin only works on fabric, soldiers apply a topical repellent (usually 25 to 30% DEET) to hands, face, and neck.
Layer three: permethrin-treated bed nets for sleeping in the field.
The Army’s MilTICK study measured how well this works. Without permethrin-treated uniforms, 27% of ticks found on soldiers had become engorged. With permethrin, only 12% were engorged. Permethrin on clothing also outperformed DEET on clothing for tick protection specifically.
The Canadian gap
The Canadian Armed Forces use a similar approach, treating garments with a soaking method using diluted 40% permethrin. But there’s a frustrating gap for Canadian civilians.
In Canada, permethrin-treated clothing is only marketed for mosquito prevention, not ticks, even though it’s the same product doing the same job. The 0.5% permethrin spray for DIY clothing treatment isn’t easy to find here. The Canadian Lyme Disease Foundation calls permethrin “an underused tool for prevention” in Canada.
For Ontarians, pre-treated outdoor clothing (available from brands like Insect Shield) is the easier option. If you’re walking trails in the Halton Region during peak tick season, permethrin-treated pants and socks combined with DEET on exposed skin is the closest you can get to military-grade protection.
What this means for your dog
Your dog can’t wear permethrin-treated clothing, but the layered-protection principle still applies. The canine version is a vet-prescribed oral preventative combined with regular tick checks and yard management.
And a reminder: permethrin is extremely toxic to cats. Never apply permethrin-containing products to or near your cat.
For a comparison of all repellent options including natural ones, see our post on the number one tick repellent.
Key takeaways
- The military uses a layered system: permethrin on clothing, DEET on skin, treated bed nets.
- Permethrin kills ticks on contact within the fabric. It doesn’t just repel them.
- Permethrin-treated clothing is underused in Canada. Pre-treated outdoor clothing is the easiest option.
- The layered approach applies to dogs too: oral preventative, tick checks, and yard management.
- Permethrin is extremely toxic to cats. Keep it away from feline pets.
References
- U.S. Army. “MilTICK Study Finds Use of Permethrin-Treated Uniforms Can Reduce Tick-Borne Illness Risk.” army.mil
- DoD Insect Repellent System. ph.health.mil
- U.S. Army. “Permethrin-treated uniforms protect against lethal diseases.” army.mil
- CanLyme. “Permethrin: An Underused Tool for Prevention.” canlyme.com
- Schreck, C.E. et al. “Comparative field evaluation of permethrin and DEET-treated military uniforms.” PubMed