I have heard claims that garlic repels mosquitoes.
Specifically, this site claims that
Eating a diet heavy in onions and garlic can make you unattractive to mosquitoes.
Is there any evidence supporting that claim?
My answer is that it is a myth. To quote this study:
The above comes from:
Comparative Efficacy of Insect Repellents against Mosquito Bites Mark S. Fradin, M.D., and John F. Day, Ph.D. N Engl J Med 2002; 347:13-18July 4, 2002
Garlic does contain some essential oils that are larvicidal to mosquitos (i.e., the oil will kill mosquito larvae on contact). Therefore, there might be a chance that rubbing garlic on one's self might repel mosquitos, however, the smell would likely also repel humans ;-)
As for whether or not eating garlic provides any significant repellence to mosquitos, a double-blind placebo controlled trial of garlic as a mosquito repellant by Rajan, et al., concluded the following
The authors did note, however, that prolonged ingestion of garlic was not studied.
According to this site (http://www.garlic-central.com/mosquito.html) it does indeed work (and here's another one http://www.mosquito-netting.com/2007-09-natural-mosquito-repellent.html). Neither of them reference any scientific study though, and a quick search didn't turn one up (but it could of course be such things are too old to be on the net).
And another one: http://www.wildernesscollege.com/plants-that-repel-mosquitoes.html
Here's a site (one of many) selling garlic based mozzie repellant: http://www.mosquitobarrier.com/
However this site (http://americanfolklore.net/folklore/2010/10/garlic_superstitions_folklore.html) lists it under folklore, but again without reference.