My experience and practice with Permethrin — without Lyme Disease

In order to reduce my likelihood of being bitten by a Black-legged Tick and possibly contracting Lyme Disease, I take behavioural precautions. I have taught outdoors most of my career, and have known about Lyme Disease since I spent the summer of 1989 in Illinois where locals were very concerned about this new threat in their area. Over the years I have turned to wearing light-coloured long pants and long-sleeved shirts, and broad-brimmed hats, both for sun coverage (skin cancer), and against ticks. I now tuck my pants into socks (and often wear short gaiters with a similar function).

Last year, when I thruhiked the Bruce Trail from Niagara Falls to Tobermory, I took several additional steps that I am now continuing, and that I am encouraging all the outdoors people that I know to adopt.

I now treat my April to November outdoor clothing with Permethrin, a residual contact insecticide that kills ticks (and many insects) on contact. I do what I can to stop ticks from getting onto my skin, so that they don’t get the chance to attach to me and possibly infect me with the Lyme Disease bacterium, Borrelia burgdorferi.  

Last year, I used a 0.5% solution of Permethrin that I sprayed onto my outdoor clothing and let it fully dry. The permethrin imbeds itself into the threads of the fabric and sticks there as a residual insecticide and acaricide. Treated clothes hold onto the permethrin for about 6 washings. (I therefore tolerate somewhat dirtier outdoor clothing than before …) I treated my shoes, gaiters, socks, pants, long-sleeved shirt(s), jacket, hat, gloves, pack, and hammock/tent. I sprayed it outdoors on a calm day — although this year I’m going to apply it in my garage. I hung my clothes to dry for a day and more. I wear this treated clothing whenever I’m going into tick territory. 

I also still do daily tick checks, and when I shower, I pay attention to fully feeling all of my body surfaces for bumps that shouldn’t be there. (Showering carefully — because our hands are very sensitive to touch — is evidently one of the most effective ways of doing body tick checks.) I choose not to put my permethrin-coated clothing into a warm/hot dryer before washing (which is a recommended practice for non-treated clothing). Putting treated clothing into dryer at is one way to knock the permethrin molecules off the clothing. Similarly, after washing, I prefer to hang my treated clothing to dry rather than using a dryer.

Permethrin has a low toxicity to humans and most other animals. It is toxic to cats when it is wet (so let your clothes dry fully before you expose any cats to them). It is toxic to fish, so fisher-people should not use it around water.  

Permethrin-treated clothing is recommended by Canada’s Travel section for travel abroad into insect- and tick-infested countries. https://travel.gc.ca/travelling/health-safety/insect-bite  Permethrin-treated clothing has been used by Canadian Armed Forces for decades, as well as by other military forces around the world. A 5% permethrin cream is recommended by Canada Public Health as appropriate for lice and scabies, including for young children. Have you ever been on an aircraft going to or coming from the Caribbean and had the interior of the plane sprayed by an insecticide while you are in the cabin? That’s permethrin!

Despite this, permethrin is not available in Canada, unless you get a permethrin cream for lice or scabies, or unless you have an agricultural pesticide licence (in which case you can buy a 10% permethrin solution for veterinary use to be applied directly to horses). Permethrin treatments are commonly used in veterinary practice for dogs and for horses (but not for cats).

So in order to get 0.5% permethrin to spray-treat my clothes, I have have to get it shipped from the United States. I have had Sawyer 0.5% spray and Ultrathon 0.5% spray shipped via Amazon.com (but NOT the Canadian Amazon.ca store!) It came through Customs without a hitch. (Your luck may vary …)  You can also get it shipped to an American contact — or have them go to a local outdoors store — and then bring it across the border yourself.  

 • https://www.amazon.com/Sawyer-Products-SP657-Permethrin-Repellent/dp/B001ANQVYU/ref=sr_1_1?ie=UTF8&qid=1491080797&sr=8-1-spons&keywords=permethrin+spray&psc=1 (Check around for different prices. Sawyer is the brand recommended by long-distance backpackers. I have also used Ultrathon 0.5% permethrin spray from 3M. One 12oz spray bottle supposedly treats two complete outfits, and I think I paid about US$15. I used two bottles for two sets of extra-large clothing as noted above.

 • I have also bought a 10% permethrin solution via Amazon.com that is exactly what I could buy at the local farmers supply store if I had an agricultural licence.  

There is another method of applying permethrin to clothing. That is to soak the clothing in 0.5% permethrin solution, and then hang to dry. The advantages include reduced spray drift, and therefore a more safe and efficient use of the material. One recommended approach is to put each piece of clothing into a separate sturdy plastic bag, i.e., big ziplock bag, and put a sufficient amount of the 0.5% solution into each bag, and massage the liquid through the clothing, leaving it in the bag for several hours before hanging to dry. I diluted that 10% solution 20:1 with water, so that I end up with a 0.5% solution. I found that using 500ml water to dilute 25ml 10% permethrin gave me enough liquid to treat a pair of long nylon pants. I have just applied it. As some people have reported, there’s a slight oily smell from this formulation. I have found that airing the clothing out of the sun for several days removes most of the smell. 

Check out http://www.tickencounter.org/prevention/soak_method (University of Rhode Island) for further information about tick-repellent clothing, including videos on the various methods of applying Permethrin.

There is yet another approach to getting permethrin-treated clothing. That is to buy from Insect Sheild in North Carolina. They have developed a proprietary method in which the clothing is treated in such a manner that the permethrin is certified to last through 70 washings — which is effectively the life of a garment. This is how the various military forces get their permethrin-treated uniforms. Guess what? Insect Shield does not ship their clothing to Canada — only to USA addresses. The other companies that also sell permethrin-treated clothing (treated by Insect Sheild) likewise do not sell or ship their permethrin-treated clothing to Canada. Know any American friends? Or anyone coming back soon from the USA?

To me, this difficulty of using the proven deterrent of permethrin-treated clothing is yet another avenue that Lyme Disease advocates need to work on. Get 0.5% permethrin clothing spray legalized. Allow permethrin-treated clothing to be imported and sold in Canada.

BTW, there is an alternative to DEET for those (like me) who detest the oily feel of DEET, and its plastic-dissolving abilities. Picaridin is an excellent insect repellent, and can be sprayed on shoes, socks and pants as a repellant (but not an insecticide/acaricde) against ticks and insects. It is becoming more available. I buy mine through Mountain Equipment Coop and other specialized outdoors stores. I am so relieved not to have to use DEET. BUT the short-term repellant value of Picaridin and DEET applications are NOT in the same league of effectiveness as permethrin-treated clothing which kills ticks.  

Last Spring I also got a prophylactic prescription for doxycycline from my family physician after I demonstrated to her that I know about Lyme Disease, Borrelia, and Black-legged Ticks, and after I showed her the precautions I was taking. I presented her with several articles, including the American Centre for Disease protocol for Doxycycline as an immediate response to engorged ticks. (I should also have directed her to the Lyme Disease Canada site: https://canlyme.com ) She took overnight to do more research, and then gave me a prescription that I filled and carried with me, to be used only if I were to find an engorged tick on my body. I would then take the Doxycycline and as soon as I could get off the trail, report to her for next steps, presenting her with the tick and the other details. I never had to use the doxy …  

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8 thoughts on “My experience and practice with Permethrin — without Lyme Disease

  1. Mark: As always, educational, thorough and well written. Thanks for sharing. Should publish this. On Naturalist etc. Ron

    • I’ve wondered about that too, Ron.
      Did you see the recent article in On Nature that included Soheil and myself? Perhaps I should follow up on that …
      Thanks!

      • No. Did not see the article. Going to send your post to my family as there are ticks at Beaver lake and we have had them on us. Naturally we want to protect the little ones. Happy Easter! 🐣 Ron

  2. The possibility of getting Insect Sheild clothing, or of getting treated Ex Officio clothing, via someone in the US is an excellent option, as the industrial treatment lasts MUCH longer. I’m not aware of any of that clothing being shippable into Canada …

    • A good question … I have no answer, since I’m not an expert in the field. I will say that it would be reduced to very low concentrations by going through the washing and rinsing. If you do the math, there would be 10% of 25ml permethrin in each soak bag. I used that 2.5ml permethrin to soak one pair of pants plus another garment. (Let’s assume 1.5ml permethrin is roughly equivalent to 1.5gm permethrin.) Let’s say 1.5gm permethrin for one pair of pants. Disregarding permethrin being removed by any rainfall, and degraded by sunlight, that means that 1.5gm permethrin stays in the clothes for reportedly 6 washings. That’s .25gm permethrin lost per washing. Actually it would be less, because there’s still some residual permethrin in the clothes, just not enough to be counted as fully effective. I don’t actually know how much water is used by my modern washing machine as it goes through a cycle (including a rinse). That wash and rinse water is then diluted by all the other wastewater, then degraded by the microbial action of sewage treatment, and then diluted by a factor of 200 (minimally) as it is discharged into the river downstream. In other words, the dilution is huge, and the compounding opportunities for degrading are also large.
      The question then becomes what are the effects of very low concentrations of permethrin and derivatives in the ecology of aquatic ecosystems?
      I’d be interested if you come up with anything. Start with my rough calculations. Then examine the various other factors, including how effectively permethrin is degraded by various biological and biochemical factors. Then research the long-term effects of permethrin.
      My understanding is that dumping permethrin, i.e. from washing out large-scale sprayers into watercourses, is the real and understood concern for fishes, and for the invertebrates that are the base of aquatic ecosystems.
      Thoughts?

  3. Mark –
    Wonderful article. I have a solution for Canadians wanting the permethrin treated clothing. There is a series of mail and shipping facilities called Kinek. There are quite a few just across the border, so what one does is to select the most convenient location, register with them, and then have the supplier ship to that depot. Then with your Kinek number and two pieces of ID, you can collect your merchandise. I am just about to do that very thing next Saturday (April 22) to pick up a boat kit. I will report back.

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