Mosquitoes find you through a layered system of cues: your breath, your body chemistry, your skin bacteria, and even your body heat. The primary trigger is carbon dioxide, which mosquitoes can detect from 10 to 50 meters away. But CO2 just gets them in the neighborhood. From there, a cocktail of skin chemicals, visual contrast, and infrared heat guides them to exposed skin and prompts them to bite.
Carbon Dioxide: The Long-Range Signal
Every exhale you take releases a plume of CO2 that mosquitoes track like a scent trail. This is the first and most important attractant, drawing them from distances of up to 50 meters. But CO2 doesn’t just pull mosquitoes closer. Research from Caltech found that after detecting a CO2 plume, mosquitoes begin paying attention to visual features they previously ignored, like dark objects and moving shapes. Before smelling CO2, they largely ignore these cues, which keeps them from wasting energy investigating rocks or vegetation. Think of CO2 as the signal that switches mosquitoes into active hunting mode, with a memory-like effect that persists for several seconds even after the plume disperses.
Skin Chemistry and Sweat
Once a mosquito gets closer, your skin’s chemical signature takes over. The key compounds are lactic acid and a related molecule called 2-ketoglutaric acid, both released through sweat. Combined with CO2, these chemicals don’t just attract mosquitoes to your general vicinity. They trigger landing and probing behavior, the actual process of searching for a blood vessel. Ammonia, also present in sweat, adds to the effect.
What makes this personal is that your skin would be nearly odorless without the bacteria living on it. These microbes metabolize sweat into the volatile compounds mosquitoes detect. The specific mix of bacteria on your skin determines your unique scent profile, which is a major reason why some people get bitten far more than others sitting in the same backyard. One study found that people who were highly attractive to mosquitoes had higher levels of Streptococcus bacteria on their skin compared to people mosquitoes largely ignored.
Heat and Infrared Detection
At close range, mosquitoes add a third layer of detection: body heat. Research published through the NIH found that the yellow fever mosquito can sense infrared radiation from skin-temperature surfaces at distances of more than two and a half feet while in flight. Infrared alone doesn’t trigger host-seeking behavior, but when combined with human odor and CO2, it doubled the number of mosquitoes that landed on a surface and started probing.
This system has an interesting limitation. It works best when there’s a temperature contrast between your skin and the surrounding air. In hot midday conditions, when the environment matches skin temperature, mosquitoes lose their ability to detect infrared cues. A heat-activated protein at the tips of their antennae, along with specialized light-detecting proteins called opsins, makes this sensing possible. This partly explains why mosquito biting peaks during cooler parts of the day, at dawn and dusk, when your body heat stands out more clearly against the background.
Why Some People Get Bitten More
The variation in mosquito bites between people is real and measurable. Your skin microbiome is the biggest driver of individual differences, but several other factors shift the odds.
Beer drinking increases mosquito attraction. A large study of 465 participants at a music festival found that people who drank beer were about 35% more attractive to mosquitoes than people who hadn’t consumed alcohol in the past 12 hours. Interestingly, the amount of alcohol in their system didn’t matter. The effect appeared to be binary: drinkers versus non-drinkers, not light drinkers versus heavy ones. Cannabis use in the prior 48 hours showed a similar increase, with smokers drawing roughly 35% more mosquito landings.
Blood type plays a smaller role than popular belief suggests. Some studies have found mosquitoes prefer type O blood over other types, but the difference was only statistically significant when comparing type O to type A, and experts caution that having a “winning” blood type in a controlled comparison doesn’t mean it’s always the dominant factor in real-world biting. Your skin chemistry matters far more.
One surprising protective finding: sunscreen reduced mosquito attraction substantially. People who had showered recently and applied sunscreen to exposed skin were about half as attractive to mosquitoes as those without sunscreen. Whether this is because sunscreen masks skin odors or because its chemical components are repellent isn’t fully clear, but the effect was strong.
How Mosquito Traps Use Attractants
Commercial mosquito traps exploit the same cues mosquitoes use to find you. Most effective traps combine CO2 (often generated by burning propane or releasing compressed gas) with synthetic lures that mimic human skin odor. Biogents, one of the major trap manufacturers, developed artificial scent sachets designed to replicate the natural emission pattern of human skin volatiles. These lures release a controlled blend of attractant compounds through a membrane over a period of about two months, protected from rain and humidity.
The most effective traps layer multiple attractant types. CO2 alone will catch mosquitoes, but adding a skin-odor lure and a heat source significantly increases capture rates. This mirrors how mosquitoes hunt in nature: each additional cue compounds the attraction. Traps targeting species like the Asian tiger mosquito and yellow fever mosquito are specifically calibrated for the odor preferences of those species, since both are strongly attracted to human-specific compounds like lactic acid.
What Actually Reduces Your Attractiveness
You can’t eliminate CO2 from your breath or fundamentally change your skin microbiome, but you can reduce the intensity of the chemical signals mosquitoes follow. Showering removes the buildup of bacterial metabolites on your skin, temporarily lowering your odor profile. Applying sunscreen appears to cut attraction roughly in half. Avoiding alcohol before spending time outdoors removes a measurable increase in biting risk.
Wearing light-colored clothing helps at the visual stage of mosquito hunting, since mosquitoes are more drawn to dark, high-contrast objects after detecting CO2. And timing matters: if you can avoid peak activity periods at dawn and dusk, you reduce exposure during the hours when the temperature contrast between your body and the environment makes infrared detection most effective.