Permethrin was originally extracted from chrysthanthemum flowers in the 1940's by Imperial Chemicals (the agricultural product division was merged into Syngenta about 1995) but now is synthesized. It is a safe and effective insecticide.
Here's something that is pretty cool. Gash a cherry or pear tree and it will exude a sticky, viscous gum over the period of two weeks. The tree produces this exudate to prevent insects from laying eggs and boring into the gash (insect pheromone repellent).
Take a knife and remove the exudate. And then apply it to the ends of your pants, shirt and collar (it will not harm clothing). I've never gotten ticks in my life. It sometimes really works well with blackflies, too, depending upon the weather. Just don't put it directly on your skin. Under the right conditions, you'll get a reaction that is really itchy.