Mosquitoes are attracted to the CO2 that we exhale. If you are a heavy breather, stand next to someone who breaths heavier than you do. Works for me...hubby breaths deeper than I do, so they get him, and leave me alone. Not such a good thing when you are diving, tho.
Also, there is a product that is sold at Orvis called REPEL permanone. You spray it on your clothes, not on your skin, and it kills and repels ticks and mosquitoes. I know others who have used it and swear by it...you don't have anything to be absorbed which could be dangerous later.