Permethrin Insect Spray

A guide to permethrin insect spray for backpacking clothing and gear treatment.

Updated on January 19th, 2021
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What is Permethrin?

Permethrin is an insecticide most commonly used to treat clothing, fabric and gear. It is a synthetic version of Pyrethrin, a naturally occurring insecticide extract from the Chrysantemum flower. This is nature's way of protecting plants from insects by killing them, rather than just repelling them.

It was discovered in 1973 and is listed as an Essential Medicine by the World Health Organization. Yep, in addition to insecticide, permethrin is actually used as a medicine to treat scabies and lice. The military later discovered it can be used to spray gear and kill insects in comes in contact with. Now, all outdoorsman, from backpackers to hunters, use it as the first line of defense against pesky bugs. 

Why Should You Use Permethrin?

Bug spray should be enough, right? Could be. Note bugs can carry some serious life-threatening diseases though. The more preventative measures you take, the less likely you are to be bitten, and the less likely you are to contract something nasty.

Once an insect comes into contact with surfaces properly treated with permethrin, their neurological system shuts down, they fall off and die. Sad day for the bug, but killing it might save your life.

Mosquitoes, black flies and ticks, particularly common in the backcountry, can carry Malaria, Dengue Fever,Rocky Mountain Spotted fever, Japanese encephalitis, Chikungunya virus, and the Zika virus to name a few. 

Due to it's widespread distribution, Lyme Disease might be the worst of them all. Lyme disease carrying ticks now infest half of the United States, with around 300,000 Americans diagnosed with this debilitating illness each year. Having tripled in the last 2 decades, Lyme disease is now the most commonly report vector-borne disease in the Northern Hemisphere. If caught in its early stages the disease can be treated with antibiotics but for long-term infections there are dire consequences such as joint stiffness, nerve pain and brain inflammation.

permethrin spray for insect mosquitoes on clothing

© turkletom(CC BY 2.0)

How Effective is Permethrin?

Permethrin's effectiveness as a bug killer is undisputed. It works well on mosquitoes, chiggers and most other arthropods (an invertebrate animal having a segmented body and jointed appendages), killing them once they travel over a fabric that has been sprayed with permethrin. 

Treated correctly as per directions with the product, your clothes or gear will be bug-proof from 4 to 6 weeks in spite of weekly detergent washing and non-washable items will retain their effectiveness for up to 42 days.

When permethrin was used in conjunction with a DEET or picaridin repellent, one study showed 99.9% protection from mosquitoes in a situation where an unprotected person would have received an average of over 1,000 bites per hour. In short, the combination is super effective if applied properly and consistently. 

Other benefits of treating your clothes and gear:

  • It is an odorless way to have protection from the nasties.

  • It won't stain or damage the fabric, including plastics or finished surfaces.

  • It will reduce the number of flying insects in your camp area.

  • Ticks can't attach themselves to you via your clothes.

Permethrin vs Deet vs Picaridin?

As a part of your overall bug protection, permethrin is only one safeguard. Permethrin will cover your clothes and your gear to keep you safe by killing the bugs on contact, but you will still need something on your exposed skin to repel the marauding bugs away from you. Insect repellents containing DEET or picaridin should be used. Unlike permethrin, DEET and picaridin insect sprays and lotions are designed to prevent contact at all.

The odorless picaridin (a synthetic compound resembling "piperine" found in plants producing black pepper) won't feel as oily on your skin as DEET products do. It is (debatably) just as effective as DEET. Picaridin also does not have the same neurotoxicity as DEET, potentially making it a safer option. Manufacturers such as Cutter, Sawyer and AVON to name a few produce insect repellents with picaridin in them.

permethrin deet picaridin spray

© Fairfax County (CC BY-ND 2.0)

Is Permethrin Safe?

Permethrin is generally considered safe to use so long as 1. you follow the manufacturer's instructions on how to use it and 2. don't eat it, breathe it in, or get it on your skin or in your eyes.

A small percentage of people who come into contact with permethrin may have minor skin redness and irritation, but reactions to it are very rare. For humans, it has a low toxicity and is poorly absorbed through the skin, hence the use of permethrin in the treatment of head lice and nits, scabies and ticks. It is dangerously toxic to animals though - so don't have your cat or dog around when applying it to your gear. 

If ingested permethrin does move quickly through the human body and leaves after a number of hours via your body's natural expelling functions. Long term exposure to permethrin is classed by the International Agency for Research on Cancer as "not classifiable as to its carcinogenicity to humans". In other words, it is still open for debate due to inconclusive testing on animals. Overall, to be safe, please just don't ingest permethrin or sprinkle any on your dinner.

How to Treat Clothing with Permethrin?

permethrin spray for clothing

Permethrin is most commonly sprayed on hiking clothing, but is also sprayed on all sorts of outdoor gear items like sleeping bags, tents, nets, hats, backpacks, sleeping bag liners and hammocks.

STEP 1: Hang items on a dryline suspended in the air outside. Spread items on a flat surface if dryline is unavailable.

STEP 2: Hold the can or bottle about 6 to 8 inches away from fabric surface and spray in a swaying, zig-zag motion. Pay close attention to cuffs and collars. Don't forget to spray the other side!

STEP 3: Double check instructions of product. But, usually items will need to dry for about 2 hours in dry climates and about 4 hours in more humid climates.

A few notes and tips:

  • Avoid spraying near lakes, ponds, your pets, or a person.

  • Ideally, you should spray items new before worn or used.

  • Store items in a resealable plastic bag to make them last longer until needed.

If you can't be bothered treating your clothes or gear with permethrin yourself, there are factory-produced options. Made by several manufacturers such as Insect Shield and Burlington as well as sold under brand names like L.L.Bean and ExOfficio, some work better than others and none are as foolproof as doing it yourself.

Suggested Permethrin for your clothing and gear: Sawyer Permethrin Spray

Suggested repellent for you skin: Sawyer Picaridin Spray or Sawyer Picaridin Lotion.

Chris Cage photo

About Chris Cage

By Chris Cage Chris launched Greenbelly Meals in 2014 after thru-hiking the Appalachian Trail for 6 months. Since then, Greenbelly has been written up by everyone from Backpacker Magazine to Fast Company. He wrote How to Hike the Appalachian Trail and currently works from his laptop all over the globe. Instagram: @chrisrcage.
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