I've not tried these myself, but supposedly lots of vitamin B12 taken a day or two before exposure to mosquitoes makes you smell bad

I tried B12 back in Massachusetts (where the mosquitoes are the size of Messerschmidts) and it does nothing. Since then, I've seen B12 pretty solidly discredited. The part about making you smell is true, though. At least I hope that's what it was.

lot less of a health risk than all the nasty chemicals that skeeters inject into you while sucking you dry.

That's a good point. West Nile fever is becoming a fact of life in the West, just as is has been for several years in the East. Dengue fever is an occasional issue in Hawaii, although I don't think it's turned up here yet. Just a matter of time, I'd wager. Deer ticks carry their own hazards as well--think Rocky Mountain spotted fever. While the odds are pretty low that any given bite is infectious, nobody has ever recommended one of these illnesses to their friends.