The female mosquito requires a blood meal to acquire the necessary proteins for egg production. For many people, it appears that mosquitoes are not equal-opportunity biters, raising a common question about whether one’s underlying biology, specifically blood type, plays a role in this attraction. The complex interaction of chemical and physical signals determines which individual becomes a target.
The Science of Blood Type Preference
Current scientific evidence suggests that mosquitoes do exhibit a measurable preference for certain ABO blood types when selecting a host. Studies have generally indicated that individuals with Type O blood are more attractive to some mosquito species, such as Aedes albopictus, than those with other blood types. This preference is often compared to Type A individuals, who are typically found to be the least attractive, while Type B and Type AB fall somewhere in the middle of this attraction spectrum. The mechanism behind this preference does not involve the mosquito sampling the blood itself before biting.
The attraction is linked to an individual’s “secretor status,” meaning the presence of ABO blood group antigens in bodily fluids like saliva and sweat. Approximately 80% of the population are secretors, meaning they secrete the chemical markers corresponding to their blood type onto the surface of their skin. Mosquitoes can detect these secreted oligosaccharides, which identify the host’s blood type before the insect lands. For Type O individuals, the secreted substance is the H antigen, which some research suggests may be a more appealing chemical cue than the A or B antigens produced by other blood types.
Primary Factors in Host Detection
While blood type contributes to the final selection of a host, it is only a close-range factor in the mosquito’s overall search strategy. The initial, long-range cue that alerts a mosquito to a potential meal is the detection of exhaled carbon dioxide (\(\text{CO}_2\)). Mosquitoes can detect plumes of \(\text{CO}_2\) from distances as great as 50 to 100 feet, using specialized receptors on their antennae. This gas is a universal signal of a breathing, metabolically active host, and its concentration guides the insect to the general vicinity of a potential target.
After detecting the \(\text{CO}_2\) plume, the mosquito transitions to using mid-range and short-range cues to pinpoint the host’s exact location. Body heat and moisture are key components of this next phase. The warmth radiated by a body, which is significantly higher than the ambient air temperature, provides a clear thermal signature for the insect to follow. Moisture, often in the form of water vapor from breath or sweat, also helps the mosquito confirm the presence of a living organism nearby.
Chemical Signatures and Genetic Influence
The final selection of a host is often dictated by the unique blend of chemical signatures emanating from the human skin surface. The composition of the skin microbiota, the community of bacteria and fungi on the skin, plays a substantial role in this process. These microorganisms metabolize compounds in human sweat, producing a complex cocktail of volatile organic compounds (VOCs) that form a distinct and highly attractive body odor. Individuals who are “mosquito magnets” often produce significantly higher levels of certain VOCs, such as carboxylic acids, which are highly attractive to mosquitoes.
The concentration of lactic acid in sweat is another close-range attractant, as mosquitoes have receptors specifically tuned to detect this chemical. Humans who naturally excrete higher amounts of lactic acid, often related to intense physical activity or higher metabolic rates, may inadvertently increase their attractiveness. The tendency to be highly attractive to mosquitoes is believed to have a heritable, genetically controlled component. This genetic influence affects the types and amounts of chemicals, including acetone, steroids, and other specific skin odors, that are released, ultimately creating an individual’s unique scent profile.