A dead tick can’t bite you—and the single-best way to terminate them in the field is to treat your shoes and clothing with permethrin, which will kill ticks rapidly on contact. (Once you’re back home, you can also crisp ticks to death with a quick spin in the dryer.)
A variety of permethrin-based products are available to treat your clothing. The simplest to use and apply are spray-on treatments, such as Sawyer Permethrin Sprays ($16 for 24 ounces), Repel Permethrin Clothing and Gear Insect Repellent ($6 for 6 ounces), and Coleman Gear and Clothing Permethrin Insect Repellent Aerosol ($7 for 6 ounces).
Here’s the important thing to know: Permethrin is not like other repellents that you apply directly to your skin and clothing on a moment’s notice. Instead, you need to treat your clothing in advance in order to give the treatment spray time to dry, a process that takes about two to four hours, depending on humidity. Once dried onto the clothing, permethrin bonds with the fabric and will last for roughly six washings before you need to re-apply.
Again, you should never apply permethrin directly to your skin—it is a potent toxin and likely carcinogen that can cause adverse effects if ingested in high doses. Permethrin-treated fabrics are considered safe to wear, but you should always be careful when using and handling spray treatments. In particular, you should apply permethrin in a very well-ventilated space (or outside) where it can rapidly dissipate. Also be aware that permethrin is very toxic to cats and aquatic life—take care if you have any fish or feline friends at home.
One last tip: If you treat only one item of clothing with permethrin, make it your shoes. Ticks—especially tiny nymph ticks—often lurk in the leaf litter on the forest floor and start their journey to your flesh by grabbing hold of your footwear and climbing upward. They don’t get far if they’re dead.