Mosquito bites are a familiar annoyance, often leading to questions about why some individuals seem to attract more insects than others. This leads to an exploration of the various scientific factors that influence insect attraction to humans.
The Blood Type Question
Human blood is classified into four main types: A, B, AB, and O, based on the presence or absence of specific proteins, called antigens, on the surface of red blood cells.
Around 80% of people are “secretors,” meaning they secrete these blood type antigens into other bodily fluids, including sweat and saliva. Mosquitoes can detect these secreted antigens on the skin, which provides them with information about a person’s blood type.
Scientific research suggests mosquitoes may show a slight preference for individuals with Type O blood, with studies indicating more mosquitoes land on Type O compared to Type A, and Type B in an intermediate range. However, this preference is often marginal and not consistently observed across all research or mosquito species. The exact mechanisms behind any blood type preference are still under investigation.
Key Attractors Beyond Blood Type
While blood type might play a minor role, several other factors are far more significant in attracting mosquitoes and other biting insects. These elements, often working in combination, determine who gets bitten most.
Carbon dioxide (CO2) is a primary long-range attractant for mosquitoes. Mosquitoes can detect plumes of CO2 exhaled from human breath from distances up to 150 feet, using specialized receptors on their antennae. Individuals who exhale more CO2, such as larger people, those exercising, or pregnant women, tend to be more attractive.
Body heat also draws mosquitoes closer. Mosquitoes use specialized sensors to detect the warmth radiating from a body, especially as they get within a few inches. They are particularly drawn to temperatures close to human body temperature.
Chemicals in sweat and on the skin are powerful attractants. Lactic acid, uric acid, and ammonia, excreted through sweat, are highly appealing, with lactic acid being a particularly strong attractant.
The unique blend of volatile compounds produced by the bacteria on a person’s skin, known as the skin microbiome, significantly influences attraction. The type and diversity of these bacteria create specific scents that can either attract or repel mosquitoes.
Movement and visual cues also contribute to a person’s attractiveness to insects. Mosquitoes can detect movement from a distance, and dark clothing, such as black, navy, or red, can make individuals more visible and appealing because these colors absorb heat and stand out against the environment. Once CO2 is detected, it can activate a mosquito’s visual system, guiding them towards a potential host.