Mosquitoes are a common nuisance, and many people observe that these insects seem to prefer some individuals over others. A widespread belief suggests that people with Type O blood are particularly attractive to mosquitoes. Scientific investigations have explored this anecdotal evidence, examining whether blood type plays a discernible role in their host preferences.
The Link Between Blood Type and Mosquito Attraction
The idea that mosquitoes prefer Type O blood has been examined in scientific studies. A key concept is “secretor status,” where most people secrete blood type antigens into their body fluids like sweat and saliva. Individuals with Type O blood who are secretors release a precursor called H antigen. Mosquitoes may sense these antigens as they approach a person.
Early research from 1972 and 1974 indicated that mosquitoes preferentially fed on people with Type O blood. A 2004 study investigated both blood type and secretor status, finding that more mosquitoes landed on people with Type O blood compared to other types. This preference was clear when compared to Type A. The same study observed that mosquitoes landed more often on Type O secretors than on Type A secretors.
More recent findings continue to support a preference for Type O blood. A 2019 study, for instance, provided mosquitoes with different blood type samples in feeders, and they consistently chose the Type O feeder more than others. While evidence suggests mosquitoes may be more attracted to Type O blood, the exact reasons are not fully understood. Theories propose mosquitoes might prefer the unique H-type antigen secreted by Type O individuals, or be less attracted to the A and B antigens found in other blood types. Blood type is one of several factors influencing mosquito attraction.
Beyond Blood Type: Other Attractants
Beyond blood type, mosquitoes are drawn to a variety of other cues emitted by humans and animals. Carbon dioxide (CO2) is a primary attractant they can detect from up to 150 to 164 feet away. Individuals who produce more CO2, such as those exercising, larger people, or pregnant women, tend to be more attractive. This respiratory output acts as a long-range signal, guiding mosquitoes toward potential hosts.
Body heat also plays a role in attracting mosquitoes. Mosquitoes can sense the warmth emanating from a body, and higher body temperatures, like those observed in pregnant women, can increase attractiveness. Chemical compounds in sweat are also lures. Lactic acid, produced during physical activity, is a notable attractant for these insects.
Other volatile compounds in human sweat and skin secretions further contribute to a person’s unique odor profile, making them more or less appealing. These include ammonia, octenol (1-octen-3-ol), and various carboxylic acids. The specific composition and diversity of bacteria on human skin also influence body odor, which in turn affects mosquito attraction. Additionally, mosquitoes use visual cues such as movement and the color of clothing, with darker colors appearing more attractive.
How Mosquitoes Sense Their Prey
Mosquitoes use a complex sensory system to locate their hosts, relying on specialized organs. Their antennae serve as primary detectors for carbon dioxide and other volatile organic compounds. These feathery appendages are covered with hair-like structures called sensilla, which house olfactory receptor neurons. Recent research also indicates that antennae contain heat-sensitive receptors and can detect infrared radiation.
The maxillary palps, located between the antennae, are important for detecting carbon dioxide. These palps contain specialized olfactory receptor neurons that are very sensitive to CO2 concentrations. These same neurons also play a role in detecting human skin odorants, highlighting their dual function in host seeking. This combination of CO2 and skin odor detection allows mosquitoes to pinpoint a host.
Mosquitoes also employ thermal sensors to detect body heat, including infrared radiation emitted from human skin. These sensors, located on the antennae, assist in guiding the mosquito once it is closer to a potential host. The integration of these diverse sensory inputs—olfactory signals, thermal cues, and visual information—enables female mosquitoes to navigate towards a blood meal.