Permethrin-treated clothing causes “hot foot” effect in ticks

Several studies have found that wearing permethrin-treated clothing can reduce the risk of tick bites. But very few studies have looked at the behavior of a tick when it comes in contact with permethrin-treated clothing. Does it climb onto the insecticide-soaked textile or avoid it entirely? Does permethrin actually kill ticks?

 

by Daniel J. Cameron, MD, MPH

Article updated: 4/25/2019

The effectiveness of permethrin treated clothing in repelling ticks has been demonstrated in several studies. A recently published study recruited state and county park employees from North Carolina to wear long-lasting permethrin-impregnated (LLPI) clothing. The authors found that the clothing “retained permethrin and bioactivity against ticks after three months of use in real-world conditions.” [1]

Another study in Rhode Island concluded that people wearing permethrin-treated sneakers and socks were 73.6 times less likely to have a tick bite than those wearing untreated footwear. [2]

But what is the actual behavior of ticks when they encounter permethrin treated clothing? How did they react? Using a model that mimicked a pant leg or the arm of a long-sleeved shirt, scientists studied the behavior and fate of ticks when exposed to permethrin-treated clothing. [3]

“Ticks approaching a textile impregnated with a strong non-contact spatial repellent (DEET) very rarely made physical contact with the treated textile,” according to Eisen and colleagues from the Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases at the Centers for Disease Control and Prevention in Colorado. [3] However, permethrin-treated textiles did not repel ticks without contact, as seen with DEET. In fact, the majority (88%) of nymphal ticks chose to move onto permethrin-treated textile versus DEET-treated textile.

After coming in contact with the treated clothing, the ticks dislodged through a “hot-foot” effect. “Ticks readily walked onto a permethrin-treated textile,” states Eisen.

But the “laboratory-reared ticks became visibly agitated, displaying a hot-foot effect, and escaped contact with the permethrin-treated textile by tumbling downwards until they dislodged themselves completely from a textile-covered assay card.”

Unfortunately, field-collected ticks were hardier than laboratory-reared ticks and able to sustain longer contact with the treated textile. The authors postulated that field-collected ticks have been exposed to highly variable temperatures and humidity conditions which may result in slower absorption of permethrin.

“However, by 1 and 24 hours post-exposure very few ticks displayed normal movement, thus presenting minimal risk to bite, regardless of whether they were reared in the laboratory or collected in the field.”

“Contact with permethrin-treated textiles negatively impacts the vigor and behavior of nymphal ticks for >24 hours,” according to Eisen, “with outcomes ranging from complete lack of movement to impaired movement and unwillingness of ticks displaying normal movement to ascend onto a human finger.”

One day after exposure, a majority of ticks were completely motionless. The remaining ticks were able to recover. “Ticks having recovered normal movement 1 day after exposure in our study most often ascended onto a finger when given the opportunity (and presumably also were capable of biting),” Eisen points out.

“In a real-life scenario, prolonged periods of time where ticks having fallen off a human host after contact with permethrin-treated textile are unable to move will undoubtedly increase the risk of mortality due to desiccation or predation.”

“A scenario more difficult to address in a bioassay is when a tick makes initial contact with bare skin and subsequently approaches loose-fitting summer-weight permethrin treated garments, such as shorts or a T-shirt,” states Eisen.

“In this case, the tick may walk underneath the treated textile and be contacted primarily from the dorsal side as the person moves and the clothing comes in and out of contact with the tick and the person’s skin.”

Permethrin is acutely toxic in high doses. The authors did not address the potential toxicity of permethrin to humans. “Acute signs of toxicity to the central nervous system include incoordination, ataxia, hyperactivity, convulsions, and finally prostration, paralysis, and death,” according to a review by the National Research Council (US) Subcommittee to Review Permethrin Toxicity from Military Uniforms. [4]

Note: Users have been advised not to inhale permethrin when treating clothes and not to apply permethrin to the skin.

 

Related Articles:

Only a minority of children with Lyme disease recall a tick bite

Are Lyme disease prevention methods really working?

How concerned are people about tick bites and tick-borne diseases?

 

References:

  1. Sullivan KM, Poffley A, Funkhouser S, et al. Bioabsorption and effectiveness of long-lasting permethrin-treated uniforms over three months among North Carolina outdoor workers. Parasit Vectors. 2019;12(1):52. Published 2019 Jan 23. doi:10.1186/s13071-019-3314-1
  2. Tick Encounter. http://www.tickencounter.org/prevention/permethrin
  3. Eisen L, Rose D, Prose R, et al. Bioassays to evaluate non-contact spatial repellency, contact irritancy, and acute toxicity of permethrin-treated clothing against nymphal Ixodes scapularis ticks. Ticks Tick Borne Dis. 2017.
  4. Health Effects of Permethrin-Impregnated Army Battle-Dress Uniforms (1994) by National Research Council. 1994. Washington, DC: The National Academies Press. https://doi.org/10.17226/9274. at https://www.nap.edu/catalog/9274/health-effects-of-permethrin-impregnated-army-battle-dress-uniforms. Last accessed 8/12/17.

 


5 Replies to "Permethrin-treated clothing causes “hot foot” effect in ticks"

  • Jill Padawer
    06/11/2018 (5:14 pm)
    Reply

    Very helpful research article that clarifies how permethrin works. Given this, and that on the one hand permethrin kills ticks better than does Deet… given that the ticks can crawl up under the treated clothes, do you recommend Permethrin treated sneakers and clothes or DEET? And, for women (or men) needing to be in sandles or leather/synthetic material shoes while on the grass (e.g., outdoor parties), do you think Permethrin has any effect sprayed on a hard sole sandle, unlike the material of sneakers? Was faced with this dilemma this past weekend! A 6-hr lawn party… Yikes! Thank you!

    • Dr. Daniel Cameron
      06/12/2018 (12:29 pm)
      Reply

      It took up to 10 seconds for the permethin impregnated cloth to cause the tick to drop off. The tick would appear to do well if it could contact skin in less than 10 seconds. It is also not clear if the permethrin protection would hold up after washing cloths. I am not convinced that ticks would stay on a sandals long enough to fall off when the skin is there.

  • Colleen
    06/17/2018 (12:56 am)
    Reply

    Permethrin kills ticks deet does not.
    Treat clothing with Permethrin and exposed skin with deet as a repellent.
    Studies show deet is still the best as a repellent, Picaridin second to deet and dies not soak into your skin as deet does.
    Picaridin can also be used in clothing.
    Better yet wear snug fitting treated clothing or with elastic bands to keep them from crawling up and under.
    Permethrin also looses it’s quality as days and washing pass especially if exposed to harsh sun.
    I’ve started asking party hosts if they have treated their property…
    If wearing a dress or skirt a snug pair of exercise short that have been treated under for some added protection, but the best is to do tick checks often. The longer they are in the more chance of contracting one of the tbd’s.So when you’re at a lawn party, do your tick check every time you use the rest room.
    Enjoy your summer!

  • Lynn Sheridan
    05/16/2019 (7:13 pm)
    Reply

    Avid Northern NH hiker here. We’ve been treating our clothing with permithrin for the past 2 years and have been very happy with the results. We also treat our dog with Vectra 3D which also contains permethrin and other chemicals. Also successful. Please be advised, it is extremely toxic to cats.

  • James Katz MD
    05/20/2019 (1:06 pm)
    Reply

    Permethrin is a derivative of oil of the chrysanthemum flower. The NRC statement on the toxicity of permethrin (1994) is woefully out of date. The EPA summary of evidence (2009 https://www.epa.gov/insect-repellents/repellent-treated-clothing ) concludes when used as directed it is safe for children and pregnant mothers. All 5 major species of ticks in the US are disabled or dead within 30 seconds. Armies around the world using permethrin-treated uniforms and DEET have eliminated 99% of tick-borne diseases, including Lyme.


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