Mosquitoes want to suck your blood

By Beth Leermakers

Are you a mosquito magnet? I sure am — and every morning on my dog walks, I become an all-you-can-eat buffet for the bloodthirsty little beasts.

“Love”— as in For the Love of Animals — doesn’t come to mind when we think of mosquitoes, but they deserve respect for their remarkable ability to locate hosts. Keep reading to learn how mosquitoes target their victims and what makes some people more attractive to the thirsty little vampires. 

Mosquitoes — insects belonging to the Diptera order (flies) — have been around since the Triassic Period (400 million years ago). There are more than 3500 species of mosquitoes worldwide, with more than 175 residing in North America.

Their ability to transmit disease makes tiny mosquitoes the deadliest animal. Malaria killed 597,000 people worldwide and infected 263 million people in 2023, according to the World Health Organization’s World Malaria Report 2024. About 1,700 cases of malaria are diagnosed in the U.S. each year, with most cases seen in immigrants and travelers returning from areas of malaria transmission. West Nile is one of the most common mosquito-borne diseases in the continental United States.

Only female mosquitoes bite people and animals. They need a blood meal to get the protein and other nutrients necessary for egg production and development. The mosquito’s first blood meal triggers its reproductive system to produce eggs. Mosquitoes don’t have teeth, so they “bite” with their proboscis (mouth) — a system of six thin, needle-like mouthparts that pierce the skin, find blood vessels and make it easy for mosquitoes to suck blood. Their proboscis gives mosquitoes the reputation of flying syringes. Here’s how it works. The female:

Finds a host. Mosquitoes use a combination of chemical and physical cues such as vision, taste, smell, heat and even infrared radiation to locate a host. Mosquitoes can sense carbon dioxide (exhaled by people and animals) from more than 30 feet away. As they get closer, they detect body heat, body odors (such as lactic acid in sweat) and visual cues (movement, shape and contrast).  

Locates a blood vessel using her proboscis. When she lands on a host, the mosquito uses her proboscis to probe its skin. The proboscis contains a straw-like structure (labrum) that pierces the skin and locates a blood vessel. Then she injects saliva containing anticoagulants into the host’s blood vessel to keep the blood flowing smoothly. The mosquito’s saliva also may contain pathogens such as heartworm (dogs and cats) or malaria parasites or encephalitis virus. This is how mosquitoes spread disease. Mosquitoes get infected with viruses and parasites when they bite infected people and animals. 

Sucks blood using the labrum. The siphoned blood then passes into the midgut, where it’s digested. 

Lays eggs. The blood meal provides the female mosquito with the proteins, lipids and other nutrients needed to develop eggs. After a blood meal, she rests, digests the blood and lays her eggs in stagnant water. 

What Makes Some People More Attractive 

to Mosquitoes?

Blood type. Some types of mosquitoes appear to prefer type O blood (the most common blood type in the United States). In a 2019 study, researchers offered mosquitoes different feeders that contained all four human blood types and found that the insects chose the type O blood feeder more than any other. Scientists aren’t sure why type O blood is more attractive, but it may have to do with protein or chemicals in the blood.

Body odor. Natural body odor comes from your skin, and it’s created by a blend of many organic compounds. Different mosquito species prefer different odors, and scientists are studying which body odors attract and repel various insect types. One 2022 study found that people who had higher levels of carboxylic acid (a chemical compound) are 100 times more attractive to one type of mosquito than those with lower levels.

Body size. Because larger adults exhale more carbon dioxide than smaller adults or kids, they’re easier for mosquitoes to target. One study found that pregnant women are twice as attractive to malaria-carrying mosquitoes as non-pregnant women. The researchers attributed the increased attractiveness to the fact that pregnant women exhaled 21 percent more carbon dioxide per breath and had hotter abdomens (and therefore released more volatile substances from their skin, making them easier for the mosquitoes to detect). 

Drinking beer. One study found that drinking a single beer made people more attractive to mosquitoes. Another study revealed that beer consumption increased the attractiveness of study participants to mosquitoes, but water consumption had no effect on attractiveness. 

What’s the best way to prevent mosquito bites? Eliminate sources of standing water from your yard, stay in screened areas between dusk and dawn (when mosquitoes are most active) and use a mosquito repellent. According to the Centers for Disease Control, repellents containing DEET or picaridin are the most effective.  

And be sure to keep your dog on heartworm preventatives year-round.