What Attracts Mosquitoes To Humans?

Mosquitos are attracted to humans because we are a food source for them. Initially what attracts mosquitos are a combination of our exhalation of carbon dioxide, body heat, and smell. Mosquitos are more attracted to people with Type O blood and least attracted to Type A blood, based on several studies.

“If you think you are too small to make a difference, try going to bed with a mosquito.” — Dalai Lama

You’ve probably heard that parasites like mosquitoes are attracted to, or like to bite some humans over others. This was long considered to be just a rumor, but in practice, it turns out to have some validity.

There is some evidence to suggest that this is true. What influences how attracted a mosquito is to a person? How do mosquitoes find their prey and choose which animals to feed on?

General Fact About Mosquitoes:

  • Only the female mosquitoes actually bite humans or other animals to drink their blood, male mosquitoes feet on the nectar produced by flowers.
  • Not all species of mosquitoes feed on human blood. Many mosquitoes feed exclusively on other animals such as birds or reptiles.
  • Mosquitoes require water to breed, though they don’t need much water. Mosquitoes can breed in small puddles left after rainstorms.
  • Mosquitoes can sense carbon dioxide plumes around 75 feet away, which is what makes them navigate towards their prey.

How Do Mosquitoes Sense Hosts?

Mosquitoes actually are attracted to the carbon dioxide that humans and other animals exhaled when they breathe. This is one way mosquitoes can find their prey, as they can use their other senses including vision, and thermal sensor information to determine if a potential host is nearby. To test the idea that mosquitoes are primarily attracted to carbon dioxide emissions, research was done that placed mosquitoes in a wind tunnel and controlled CO2 levels in the environment. The mosquitoes consistently navigated towards areas with CO2 plumes that mimicked the amount of CO2 released by human breath, and the presence of the CO2 plume increased the likelihood that they would approach a particular object.

What Influences Which Humans Mosquitoes Target?

Photo: Public Domain

As mentioned, carbon dioxide is one of the things that attract mosquitoes, and all species of mosquitoes have an organ referred to as the maxillary palp, which senses plumes of carbon dioxide. Mosquitoes mix this information with the information they obtain from body odor and their ability to sense heat to find potential prey. This means that those who exhale large amounts of carbon dioxide, such as adults and larger individuals will be bit more often than others.

“Mosquitos remind us that we are not as high up on the food chain as we think.” — Tom Wilson

One thing that influences which people mosquitoes go after is their blood type. At least one study has found that those who have blood type O are favored targets for mosquitoes when compared to other people who have blood type A or type B. The different blood types have different levels of sugar and other compounds, and the researchers who conducted the study believe the presence of a particular sugar in blood type O is particularly attractive to mosquitoes, though they obviously will feed on people of other blood types.

It’s also believed that the lactic acid present in skin plays some role in how mosquitoes choose their victims. Studies have found that higher levels of lactic acid in the skin increase a person’s level of attractiveness to a mosquito.

Because of the fact that an individual’s level of metabolic activity, as well as how much they exercise, influence their production of carbon dioxide and lactic acid, strenuous exercise may also make you more of a target for mosquitoes. Lactic acid, ammonia, and uric acid are all released in people’s sweat. Higher body temperatures all are also thought to attract mosquitoes, and your body temperature rises when you exercise.

Women who are pregnant may experience more mosquito bites than the average person, as they tend to exhale around 20% more breath than the average person, meaning they release about 20% more carbon dioxide. Pregnancy also increases the amount of blood near the surface of the skin, making pregnant women around 0.7°C warmer than people on average, which makes it easier for mosquitoes to sense them.

Other studies have suggested that drinking alcohol may also attract mosquitoes to people, though the study in question was a small scale study with only 13 people, making it somewhat dubious.

Though the vision of mosquitoes isn’t considered to be that strong, mosquitoes can use their vision to find targets. People who dress in colors that make them send out, such as black or red, may find themselves bitten by mosquitoes more often than people who wear more muted colors.

Even something as subtle as skin bacteria can influence how likely mosquitoes are to bite you. One particular study found that having large amounts of specific kinds of skin bacteria impacted a person’s chance of being bitten by a mosquito. This may also explain why mosquitoes often target regions of the body like the ankles and feet, which are high in bacterial colonies.

A variety of genetic factors are thought to influence how attractive an individual is to mosquitoes, accounting for up to 85% of the variance in the people’s attractiveness to mosquitoes. People whose genes predispose them to have high concentrations of cholesterol in their skin, or of steroids within their bodies, may be larger targets for mosquitoes than others.

Keeping Mosquitoes Away From You

When it comes to repelling mosquitoes, a variety of different mosquito repellents are available. However, not all of these different repellents are equally effective. For repelling mosquitoes, repellents that utilize DEET are thought to be the most effective. Repellents that have around 24% DEET concentration are effective at repelling mosquitoes for up to five hours.

Effective alternatives to DEET include the chemical Picaridin, which has grown in popularity during recent years because it tends to be as effective as DEET but does not have its distinctive odor. Oil of eucalyptus has been endorsed by the CDC as a product that offers protection against mosquito bites. Its effectiveness is similar to applying low levels of DEET to your skin.

“Mosquitos are a very important agent for transmission of zoonotic diseases… I’d worry first about mosquitos and then about water quality.” — Leon Russell

Mosquito coils, or mosquito lamps or lanterns utilize the insecticide allethrin to drive away mosquitoes. They are effective in a range of about 15 feet, though their effectiveness drops when there is wind. Exposure to the fumes from these products can be hazardous and cause irritation of the skin, so use them carefully and responsibly. Gentler alternatives to these products exist, such as citronella candles, but they have a very small effective range, generally less than 2 m (meaning you would have to sit right next to the candle all day).

One of the best ways to reduce your chance of being bitten by a mosquito is to simply reduce their numbers. Get rid of any standing water in the region around your home and you will see mosquito numbers decrease.