Citronella oil. Mix into your usual body lotion or dilute with a carrier oil to apply. You can also thin the mix down with a bit of alcohol and put it in a spray bottle.
Only trouble is, YOU have to be able to stand it yourself! It's a strong lemongrass-y smell. (It's actually one of the things Skin So Soft uses, but mixed in with other stuff to dilute; I think it used to have teatree oil too, which is soothing on bites and also just poisonous enough to keep the gnats off you.) ETA: If you can stand it, and want to go to town with this, add some oil of eucalyptus too for good measure. Great for blocked noses as well.
By the way, if your blood type is O, you're best off using something --- ANYthing --- strong-smelling to mask your natural aroma, which is absolutely tantalising to mosquitoes. Any perfume is better than au naturel if you're an O. http://www.theage.com.au/artic.....64772.html
However, beware of your regular skin products too --- mozzies love lactic acid and urea/uric acid, both popular skincare chemicals. http://articles.cnn.com/1999-0.....=PM:NATURE
Also, don't eat bananas. It's a bug beacon, apparently. Can't locate the link for this, old pre-interwebs study.