Why Mosquitoes Bite Some People More, and How to Get Bitten Less

How mosquitoes pick which person to bite

Only female mosquitoes bite, because they need protein from blood to produce eggs. A female finds a person by following a chain of cues. Carbon dioxide in exhaled breath draws her in from a distance, and body heat and skin odor guide her the last few feet. People differ in each of those signals, and some of the differences are large enough that one person draws far more mosquitoes than another sitting in the same spot.

Part of the difference is inherited. A study of twins found that identical twins were more alike in how attractive they were to mosquitoes than fraternal twins, which points to genes that shape body odor. How strongly a person reacts varies as well. The itchy welt is the immune system responding to mosquito saliva, and some people who believe they never get bitten are bitten regularly but barely react.

How carbon dioxide and body heat attract mosquitoes

Mosquitoes sense the carbon dioxide in a person's breath from a distance and fly upwind along the plume to find its source. Larger people generally exhale more carbon dioxide than smaller ones, and anyone breathing hard after yard work or a run gives off more still.

At close range, mosquitoes rely more on body heat and use it to find exposed skin. That is one reason people draw more of them right after exercise, when skin is warm and damp with sweat.

Why skin odor makes mosquitoes bite some people more

People differ most in skin odor, which is a mix of compounds made by the body and by the bacteria living on the skin. In one study of a malaria mosquito, people with a more varied mix of skin bacteria drew fewer mosquitoes than people with a less varied mix.

A 2022 study at Rockefeller University tested volunteers against Aedes aegypti, the mosquito that bites during the day in Valley yards. The people who drew the most mosquitoes had higher levels of certain fatty acids on their skin, and they stayed the most attractive when the researchers tested them again over several years. That matches what many families see, with the same person getting bitten summer after summer.

Lactic acid, which the body releases in sweat, is another known attractant, and Aedes aegypti responds strongly to it combined with carbon dioxide. Exercise raises lactic acid, body heat and breathing all at once, so an outdoor workout late in the afternoon tends to draw plenty of mosquitoes.

What research says about blood type and beer

Blood type is a common theory, and a few studies have reported that mosquitoes landed more often on people with type O blood, while others found no clear preference. The evidence is mixed, and since nobody can change their blood type, it has no bearing on what to do in the yard.

One small study in Japan found that mosquitoes landed on volunteers more often after they drank a single bottle of beer. It was a single study with a small group of volunteers, which is not enough to treat the result as a rule.

How clothing color affects mosquito bites

Mosquitoes also hunt by sight at close range, and they tend to fly toward dark colors. Light-colored, loose clothing makes a person a little harder to find and harder to bite through. Aedes aegypti often bites low on the legs and ankles, so long pants and socks cut down on bites during daytime yard work.

How to get fewer mosquito bites in Valley yards during monsoon season

Most of the mosquitoes biting in a Valley yard during the day are Aedes aegypti, and they usually come from standing water within a few hundred feet. The females lay eggs on the inside walls of containers just above the waterline. Those eggs can sit dry for months and hatch once monsoon rain or a sprinkler refills the container, and in summer heat the larvae can become biting adults in about a week.

The most useful habit from July through September is a weekly walk around the yard:

• Dump and scrub plant saucers and pet bowls so eggs stuck to the sides come off.
• Turn wheelbarrows and kiddie pools upside down, and store toys where rain cannot reach them.
• Pull tarps and grill covers tight so they do not hold water after a storm.
• Change the water in birdbaths and fountains at least once a week.
• Check irrigation valve boxes and low spots in the lawn for water that stands for days.
• Keep the pool chlorinated and circulating, and drain rainwater that collects on pool covers.

Yards that are flood irrigated, which is still done in some older neighborhoods in Mesa, Tempe and central Phoenix, should drain within a few days. A neglected pool nearby can produce large numbers of mosquitoes, and Maricopa County's vector control program takes reports of green pools. Our article on monsoon season pests covers what else the storms stir up.

For people who attract mosquitoes more than others, personal protection makes the biggest difference. EPA-registered repellents containing DEET, picaridin, IR3535 or oil of lemon eucalyptus reduce bites when applied as the label directs. A fan on the patio helps, since mosquitoes are weak fliers, and screens on doors and windows keep daytime biters out of the house.

When to call a pest control company about mosquitoes

If bites keep coming after the standing water is gone, mosquitoes may be breeding somewhere hard to see, such as a drain, a valve box or a neighbor's yard. Our mosquito control service treats the shaded places where adult mosquitoes rest, including dense shrubs, the shady side of block walls and the space under patio covers, along with water that cannot be drained. Treatment lowers the number of mosquitoes in the yard, though it cannot stop breeding on another property.

Platinum Pest Management offers a free inspection anywhere in our service areas to find where mosquitoes breed and rest around the property. Questions about a specific yard can go through our contact page.