Mosquitoes are a common nuisance. Only female mosquitoes bite, as they require a blood meal to obtain the protein and nutrients necessary to develop their eggs. Locating a host is a sophisticated, multi-stage operation driven by survival. This process involves detecting various chemical and physical signals emitted by warm-blooded animals, which guide the mosquito from a distance right up to the point of landing.
The Blood Type Question
Research suggests blood type may influence a mosquito’s preference, though it is not the only factor. Studies, including those on the Aedes aegypti species, indicate a preference for individuals with Type O blood. Type O attracts mosquitoes significantly more often than Type A, with Type B falling in between.
This preference is based on chemical signals released by the host, not the blood itself. Approximately 85% of people are “secretors,” meaning they secrete water-soluble antigens corresponding to their blood type through their skin. Mosquitoes can detect these specific chemical markers on the skin surface, allowing them to discern a host’s blood type before biting.
The Chemical Beacon: Primary Attractants
The most universal and long-range signal drawing a mosquito to a host is carbon dioxide (CO2). Mosquitoes possess highly sensitive receptors that can detect CO2 plumes up to 50 meters away. The concentration gradient of this gas, which humans exhale, acts as the primary homing signal to identify a warm-blooded target.
Once the mosquito closes the distance, attraction shifts to short-range physical cues. Body heat and moisture become the guiding factors used to pinpoint the host’s exact location. Specialized heat-sensing organs called thermoreceptors allow the mosquito to detect the warmth radiated from the skin.
Why Individuals Differ: Metabolic and Genetic Factors
Even among groups exhaling similar amounts of CO2, individuals vary dramatically in attractiveness due to personalized chemical outputs. The unique combination of bacteria on the skin, known as the skin microbiome, breaks down sweat compounds to produce a distinct cocktail of volatile organic compounds. This resulting odor profile, which includes chemicals like carboxylic acids, is a stable attractant for mosquitoes.
Physical exertion increases body temperature and the production of lactic acid, a compound in sweat highly attractive to mosquitoes. The combination of lactic acid and CO2 is effective at triggering host-seeking behavior. Physiological changes like pregnancy are associated with increased body temperature and higher CO2 output, making pregnant individuals more frequent targets. Alcohol consumption can also temporarily increase attractiveness, likely by altering metabolism and slightly raising body temperature or increasing CO2 and sweat production. Furthermore, the genetic predisposition for attracting mosquitoes is thought to be an inherited trait.
Mitigation Strategies Based on Science
Applying topical repellents is an effective way to disrupt a mosquito’s host-seeking process. The most common active ingredients are DEET and Picaridin. These compounds interfere with the mosquito’s chemical receptors, masking attractive human scents like lactic acid and CO2.
Behavioral choices can also minimize a person’s chemical signature. Since sweat and odorants are attractants, showering after strenuous exercise removes the buildup of lactic acid and other volatile compounds. Clothing color is also a factor, as mosquitoes are visually attracted to high-contrast and dark colors, which absorb heat. Opting for light-colored clothing can make a person less conspicuous to a mosquito that has already detected a CO2 plume.