I don't actually keep it in my pack. I do keep a can of the spray in the back of my truck and hit my hat, boots and sleeves every time I get out. If I don't I am crawling with them in minutes. Not sure if it's where I go or what, but they are thick. I took a friend once who didn't use the spray before leaving. I looked over when we were eating lunch and he had at least ten crawling up one arm. I've had to pull the nasty buggers out. I'll do whatever I can to avoid that.