Recently I did a 6 day kayak self-support trip on the mighty Yampa river in northwestern Colorado. I got sick when I got home. BAD sick. I think I had West Nile virus, and that it infected the meninges of my brain. But I am bouncing back, finally. The only upsides I can detect is that I lost some weight that I didn't mind losing, and that if I did have West Nile, I won't be getting it again.
A couple days ago I read the recent missive of the EWG (Environmental Working Group) about bug repellants (which we didn't have). They pretty much said that the herbal ones don't really work, and with stuff like West Nile and malaria out there, you want one that works. Hence the DEET recommendation. I have more research to do about it because I hear that there's another chemical that may be less toxic to humans and work as well as DEET, but I don't know it yet to report on it. I've heard that the clothing that is impregnated with bug stuff really works well too, so if I ever go "Yamping" again I'll take some of that.
Suffice it to say that I really recommend avoiding mosquito bites this season. Apparently it's a bad West Nile season in Colorado and in Oregon, because of the mild winter and warm spring. It's probably bad nationwide. And the disease that can be caused by West Nile is sorely unpleasant. Don't get it, but if you do get a big fever and headache after mosquito bites, get naturopathic support. Conventional docs will just tell you to take ibuprofen or acetomenophen and go to bed.