May 29, 2011 at 12:32 PM ET
Some folks seem to be magnets for mosquitoes, while others rarely get bitten. What makes the little buggers single you out and not the guy or gal you're standing next to at the Memorial Day backyard barbecue?
The two most important reasons a mosquito is attracted to you have to do with sight and smell, says Jonathan Day, a professor of medical entomology at the University of Florida in Vero Beach. Lab studies suggest that 20 percent of people are high attractor types, he says.
Mosquitoes are highly visual, especially later in the afternoon, and their first mode of search for humans is through vision, explains Day. People dressed in dark colors -- black, navy blue, red -- stand out and movement is another cue.
Once the mosquito keys in on a promising visual target, she (and it's always "she" -- only the ladies bite) then picks up on smell. The main attractor is your rate of carbon dioxide production with every exhale you take.
Those with higher metabolic rates produce more carbon dioxide, as do larger people and pregnant women. Although carbon dioxide is the primary attractant, other secondary smells coming from your skin or breath mark you as a good landing spot.
Lactic acid (given off while exercising), acetone (a chemical released in your breath), and estradiol (a breakdown product of estrogen) can all be released at varying concentrations and lure in mosquitoes, says Day. Your body temperature, or warmth, can also make a difference. Mosquitoes may flock to pregnant women because of their extra body heat.
But with more than 350 compounds isolated from odors produced by human skin, researchers have barely scratched the surface behind a mosquito's preference for certain people, says Joseph Conlon, a medical entomologist and the technical advisor to the American Mosquito Control Association.
Although it may all boil down to human odor and genetics -- studies of twins have revealed they tend to be attractive or repellant to mosquitoes in the same measure -- it's more complicated than that, suggests Conlon.
He says the latest thinking is that it might not be about what makes people more attractive to mosquitoes, but what makes them not as repellant. It could be that individuals who get less bites produce chemicals on their skin that make them more repellant and cover up smells that mosquitoes find attractive.
Mosquitoes don't bite you for food, since they feed off plant nectar, Conlon explains. Females suck your blood to get a protein needed to develop their eggs, which can then send more pesky insects into the world to annoy you.
But keep this in mind when you're outdoors this summer: Mosquitoes are more attracted to people after they drink a 12-ounce beer. It could be that people breathe a little harder after a cold one or their skin is a little warmer, suggests Conlon. But that won't stop him from having a brewski, even though he considers himself a mosquito magnet.
Here are more fun facts about mosquitoes and bites provided by our experts: