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:
Most alternatives to topically applied repellents have proved to be ineffective. No ingested compound, including garlic and thiamine (vitamin B1), has been found to be capable of repelling biting arthropods.26-28 Small, wearable devices that emit sounds that are purported to be abhorrent to biting mosquitoes have also been proved to be ineffective.29 In our study, wristbands impregnated with either DEET or citronella similarly provided no protection from bites, consistent with the known inability of repellents to protect beyond 4 cm from the site of application.
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 data did not provide evidence of significant systemic mosquito repellence.
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.