I'm being eaten alive this summer (we've had a lot of rain and there's still a lot of water in the woods)- I can't even pick one tomato from the garden without coming back with bites.

A few years ago the New England Journal of Medicine published a randomized controlled trial comparing various mosquito repellants (how they ever got volunteers is beyond me) http://content.nejm.org/cgi/content/abstract/347/1/13 - the bottom line is that DEET is the only thing that works reliably.