If you spray on permethrin at home, make sure you allow time to do the treatment according to directions, have all the necessary equipment on hand, and allow time for the fabric to dry.
My husband used to buy several bottles of permethrin a year as he spends many days outdoors year-round working and recreating in the woods on and near the A.T. around Harpers Ferry, WV. This summer, we both sent a batch of clothing to InsectShield--including Darn Tough wool socks, and synthetics. In the factory, InsectShield uses high heat to bond the chemical to the fabric, so it bonds more tightly and stays on the fabric longer than spraying on yourself at home. We wore some of the clothing on a 6-day backpack on the A.T. in Maine in July, and he has used it since then outdoors in the very hot and humid conditions we've had here in Harpers Ferry. We've been really happy with it, and have seen no ticks.
A.T. tick researcher
Karl Ford feels that wearing permethrin-treated clothing is the single most important prevention strategy for avoiding Lyme disease. You can read more about his research and advice on the WhiteBlaze thread he started
Study Results: Tick-borne Disease Risk to Appalachian Trail Hikers, Karl Ford, Ph.D.
Not everyone feels comfortable with chemicals; no one has to use permethrin. Ray Jardine, the famous pioneer of ultra-lightweight backpacking, believes in simply wearing light-colored clothing, with long pants tucked into socks and long-sleeved shirts tucked into pants, and doing frequent tick checks on clothing.
Whatever you do, educate yourself about ticks, do frequent tick checks year-round (anytime temperatures are above freezing) and know the symptoms of Lyme and other tick-borne diseases. Many hikers never see the tick that infected them, and only 50-70% (some say less) get the tell-tale bulls-eye rash.
On overgrown sections of trail you may not be able to avoid ticks, but you can be proactive about reducing your exposure to ticks by always putting a pad down when you sit on logs, leaf litter, or in grassy areas. Shelters are actually have very few ticks, since there is little vegetation for them.
(I realize most posting on this thread know all this, but writing this for newbies who may be checking this out).
Here are two videos InsectShield and ATC partnered on this spring, at Karl Ford's suggestion and under his guidance.
Preventing Tick-Borne Diseases on the Appalachian Trail
Expert Opinions on Tick Bite Prevention on the Appalachian Trail
Lyme (and other tick-borne diseases) are serious business. Not all strategies are right for everyone. The important thing is to have them.