Mosquitoes find you through a layered sequence of cues, starting with the carbon dioxide you exhale and narrowing down to your body heat, skin chemicals, and even the bacteria living on your skin. Female mosquitoes (males don’t bite) can detect these signals from several meters away, and the combination of cues you give off determines whether you’re a mosquito magnet or relatively unbothered.
Carbon Dioxide Is the First Signal
Every time you breathe out, you release a plume of carbon dioxide that acts like a homing beacon. Mosquitoes can detect CO2 and other volatile body odors from multiple meters away, and they fly upwind along that trail to reach you. This is the long-range signal that gets the process started. Larger people and those breathing heavily (after exercise, for instance) produce more CO2, which is one reason adults tend to get bitten more than children.
Once a mosquito locks onto your CO2 trail, she switches to shorter-range cues like body odor and visual contrast against the background. Think of it as a funnel: CO2 gets her into the neighborhood, your scent gets her to the right house, and your body heat guides her to the front door.
Your Skin Bacteria Shape Your Scent
The smell that mosquitoes actually home in on isn’t just your sweat. It’s largely produced by the bacteria living on your skin, which break down sweat compounds into volatile chemicals. A study published in PLoS One found that people who were highly attractive to mosquitoes had significantly more bacteria on their skin but lower bacterial diversity than people mosquitoes avoided. In other words, it’s not about being “dirtier” but about which microbes dominate.
Specifically, people with higher levels of Staphylococcus bacteria (about 2.6 times more than less-attractive individuals) drew more mosquitoes. Meanwhile, people with higher levels of Pseudomonas bacteria (about 3.1 times more than highly attractive individuals) were bitten less. The bacterial communities on poorly attractive people were roughly 38% more diverse. This helps explain why mosquitoes love to bite ankles and feet, where certain bacterial colonies thrive and produce distinct odor profiles rich in carboxylic acids and alkenes.
One chemical that especially matters is sulcatone, a volatile compound present in much greater amounts on human skin than on other animals. Mosquito species that specialize in biting humans, like Aedes aegypti, have smell receptors with heightened sensitivity to sulcatone compared to mosquito species that prefer other animals. It’s one of the key signals that makes us taste like “human” to a mosquito.
Body Heat and Infrared Detection
At close range, mosquitoes sense your body heat. Scientists long assumed this only worked through convection (warm air rising off your skin), which requires the mosquito to be within about four inches. But research from the NIH showed that Aedes aegypti mosquitoes can also detect thermal infrared radiation from more than two and a half feet away while in flight.
This infrared sensing depends on a receptor protein called TRPA1 on the mosquito’s antennae, assisted by specialized light-detecting proteins called opsins that boost sensitivity at greater distances. The system works best when the surrounding air is cooler than skin temperature, which explains something many people notice intuitively: mosquitoes seem most aggressive around dawn and dusk, when the temperature difference between your body and the environment is greatest. At midday, when ambient heat matches skin temperature, mosquitoes largely lose this infrared advantage.
Genetics Play a Major Role
If you feel like mosquitoes single you out while leaving others alone, you’re probably right, and your genes are a big reason why. A twin study found that identical twins showed highly correlated attractiveness to mosquitoes, while non-identical twins did not. The estimated heritability was 62%, meaning more than half the variation in how attractive you are to mosquitoes comes down to your DNA. When twins were tested side by side, heritability climbed even higher, to 83%.
Researchers suspect this genetic influence works through body odor. Your genes control which volatile chemicals your skin produces, which in turn shapes your skin microbiome and the scent profile mosquitoes detect. The major histocompatibility complex (a group of immune-related genes that also influences body odor) has been proposed as one possible mechanism, though studies so far haven’t pinpointed a clear link between specific gene variants and mosquito preference.
Pregnancy, Alcohol, and Other Temporary Factors
Certain temporary states make you more attractive to mosquitoes. Pregnancy is one of the most well-documented. A study in the Gambia found that women in late pregnancy exhaled 21% more air than non-pregnant women, sending out a bigger CO2 signal. Their abdominal skin was also 0.7°C warmer, giving mosquitoes a stronger heat target. The combination means pregnant women attract roughly twice as many mosquitoes.
Drinking alcohol also increases your appeal. In one controlled experiment, mosquito landing rates on volunteers increased significantly after drinking a single 350 ml beer. Interestingly, the researchers couldn’t trace this to ethanol in sweat or changes in skin temperature, suggesting alcohol alters some other aspect of your chemical profile in ways that aren’t fully understood yet. Exercise has a similar effect, likely through increased CO2 output, elevated skin temperature, and greater production of lactic acid in sweat.
What About Blood Type?
The idea that mosquitoes prefer type O blood is widely repeated, but the evidence is shaky. One study that claimed to show blood type preferences in a malaria-carrying mosquito species was retracted from the journal Scientific Reports. The few remaining studies on the topic have small sample sizes and inconsistent results, with some pointing to type O and others to type B as most attractive. Given that mosquitoes detect you primarily through airborne chemicals, CO2, and heat (they can’t “smell” your blood type from a distance), blood type is likely a minor factor at best.
How Repellents Disrupt the Process
DEET, the most effective and widely studied mosquito repellent, works primarily through the mosquito’s smell system. Rather than simply masking your scent, DEET directly activates certain odor receptors on the mosquito, producing a signal the insect finds aversive. In the southern house mosquito, DEET triggers a specific receptor that also responds to plant defense chemicals, essentially mimicking a “danger” signal. This is why DEET doesn’t just reduce landings but actively repels mosquitoes from the treated area.
Picaridin and other repellents work through similar olfactory interference, though through slightly different receptor pathways. The practical takeaway: repellents don’t make you invisible to mosquitoes. They override the “bite this human” signal with something unpleasant enough to send the mosquito elsewhere.