My chemically sensitive friend Celia would like to add that eating garlic is a great mosquito repellent for her and her family. Of course, it can be a people repellent too, but maybe that isn't such a bad thing. I have found that taking (and/or eating) plenty of B vitamins also helps.
Also, here's a website for information about pesticides on the food we eat:
www.whatsonmyfood.org (a searchable database)