Feature Archive

Are You a Mosquito Magnet?

Experts try to crack the code behind why mosquitoes like some humans more than others.

By Elizabeth Heubeck, M.A.
WebMD Feature

Reviewed By Brunilda Nazario, MD

You're flipping burgers for the neighborhood barbecue, and the mosquitoes have already begun their feast -- on you. As you swat madly at the pests, you notice other folks seem completely unfazed. Could it be that mosquitoes prefer dining on some humans over others? This may clear up the mystery.

It's true. Mosquitoes do exhibit blood-sucking preferences, say the experts. "One in 10 people are highly attractive to mosquitoes," reports Jerry Butler, PhD, professor emeritus at the University of Florida. Incidentally, it's not dinner they're sucking out of you. Female mosquitoes -- males do not bite people -- need human blood to develop fertile eggs. And apparently, not just anyone's.

Who Mosquitoes Like Best

While researchers have yet to pinpoint what mosquitoes consider an ideal hunk of human flesh, the hunt is on. "There's a tremendous amount of research being conducted on what compounds and odors people exude that might be attractive to mosquitoes," says Joe Conlon, PhD, technical advisor to the American Mosquito Control Association. With 400 different compounds to examine, it's an extremely laborious process. "Researchers are just beginning to scratch the surface," he says.

Scientists do know that genetics account for a whopping 85% of our susceptibility to mosquito bites. They've also identified certain elements of our body chemistry that, when found in excess on the skin's surface, make mosquitoes swarm closer.

"People with high concentrations of steroids or cholesterol on their skin surface attract mosquitoes," Butler tells WebMD. That doesn't necessarily mean that mosquitoes prey on people with higher overall levels of cholesterol, Butler explains. They simply may be more efficient at processing cholesterol, the byproducts of which remain on the skin's surface.

Mosquitoes also target people who produce excess amounts of certain acids, such as uric acid, explains entomologist John Edman, PhD, spokesman for the Entomological Society of America. These substances can trigger the mosquitoes' olfactory sensations, or sense of smell, causing them to launch their "landing" onto unsuspecting victims.

But the process of attraction begins long before the landing. Mosquitoes can smell their dinner from an impressive distance of up to 50 kilometers, explains Edman. This doesn't bode well for people who emit large quantities of carbon dioxide.

"Any type of carbon dioxide is attractive, even over a long distance," Conlon says. Larger people tend to give off more carbon dioxide, which is why mosquitoes typically prefer munching on adults to small children. Pregnant women are also at increased risk, as they produce a greater-than-normal amount of exhaled carbon dioxide. Movement and heat also attract mosquitoes.

So if you want to avoid an onslaught of mosquito bites at your next outdoor gathering, stake out a chaise lounge rather than a spot on the volleyball team. Here's why. As you run around the volleyball court, the mosquitoes sense your movement and head toward you. When you pant from exertion, the smell of carbon dioxide from your heavy breathing draws them closer. So does the lactic acid pouring from your sweat glands. And then -- gotcha.

Where Mosquitoes Lurk

Even if your body chemistry doesn't attract mosquitoes, where you're located might.

Some of the worst mosquito populations exist along coastal areas, Conlon tells WebMD. And being several miles inland does not guarantee your safety from the pests. "They'll fly 40 miles for a meal," Conlon says.

While any water source is potential breeding grounds for mosquitoes, they much prefer stagnant water. So if you crave a mosquito-free water oasis on your property, forego the backyard pond and seek out a babbling brook instead.

"Even in a desert area, mosquito biting tends to be intense around a water source," Conlon says.

Can you find respite high in the mountains? Don't count on it. Although they're generally not active below 55 degrees Fahrenheit, mosquitoes have been sighted in the Himalayan Mountains, Conlon tells WebMD.

How about cold climates in places such as Alaska? You're safe for most of the year. But, says Conlon, mosquitoes flock there for a brief, three-week period between July and August. "The Arctic National Refuge is one big bog," Conlon explains, making the mosquito population there second only to that in the Florida Everglades.

With a long track record -- mosquitoes have been around for 170 million years -- and more than 175 known species in the U.S., these shrewd summertime pests clearly aren't going to disappear any time soon. But you can minimize their impact.