I am getting ready to treat my clothes with permethrin. I love the stuff, and it worked well for me last year, but I don't remember if I sprayed underwear or not. Do you spray underwear? It is allegedly safe for pants and shirts when dry, so I can't imagine why underwear wouldn't work, but it seems a little scary somehow. My thought is that any ticks that wanted to wander up legs to find a home in the nether regions may crawl under contact with shorts. A somewhat tighter fitting leg of a boxer brief would really form a tick barrier. Generally speaking, I am more afraid of ticks than chemicals, but I would appreciate your thoughts.