What Blood Type Are Mosquitoes More Attracted To?

People with type O blood are bitten more often by at least one common mosquito species, but the full picture is more complicated than the viral headlines suggest. The preference varies by mosquito species, and several other factors, from the chemical cocktail on your skin to the bacteria living there, play a larger role in whether you end up covered in welts while the person next to you escapes untouched.

What the Blood Type Studies Actually Found

The study most often cited in popular media tested Aedes albopictus, the Asian tiger mosquito, on 64 volunteers. Mosquitoes landed on type O individuals about 79% of the time, compared with roughly 57% for type B, 48% for type AB, and 45% for type A. But the only statistically significant difference was between O and A. The gaps between the other groups could easily have been noise in a fairly small sample.¹

Here’s where it gets interesting: when researchers tested Aedes aegypti, the primary dengue and yellow fever mosquito, in controlled tunnel chambers, the winner was blood group B, not O.² A separate study on Anopheles stephensi, the Asian malaria vector, also found a strong preference for type B blood. Air currents carrying the scent of type B blood triggered a significantly stronger seeking response than other blood groups.³

So the claim that “type O attracts mosquitoes most” is only supported for one species in one study. For at least two other medically important species, type B came out on top. The honest answer is that blood type preference depends on which mosquito is biting you, and none of these studies have been replicated at the kind of scale that would make the conclusion airtight.

Why the Answer Changes With the Mosquito

Different mosquito species have evolved to track different chemical signals when hunting for a blood meal. Aedes albopictus, Aedes aegypti, and Anopheles stephensi don’t share the same sensory hardware. They have different suites of olfactory receptors, and they’ve adapted to different ecological niches and host animals over millions of years. The domestic form of Aedes aegypti, for instance, evolved a specialized preference for human odor linked to increased expression of a specific odorant receptor called Or4, which recognizes a compound found at high levels in human scent.⁴ A forest-dwelling ancestor of the same species prefers non-human animals entirely.

This means that one mosquito species might detect and respond to the sugar molecules (antigens) on the surface of type O red blood cells differently than another species responds to type B antigens. ABO blood type antigens aren’t just on red blood cells; people who are “secretors” (roughly 80% of the population) also express these sugar molecules on their skin and in bodily fluids. That gives mosquitoes a potential way to detect blood type before they even bite. But the strength of that detection varies by species, and the signal competes with dozens of other, stronger chemical cues your body puts out.

The Chemical Signals That Matter More Than Blood Type

Your skin is constantly releasing a cloud of volatile chemicals, and several of these are far more powerful mosquito attractants than anything related to ABO blood group. Research tracking over 1.3 million mosquito flight paths has identified carboxylic acids as a key dividing line between people mosquitoes find irresistible and people they largely ignore. Highly attractive individuals produce significantly more of certain carboxylic acids, particularly pentadecanoic, heptadecanoic, and nonadecanoic acids, along with at least ten additional unidentified compounds in the same chemical class.⁵ The least attractive people didn’t share some common repellent compound; they simply lacked the attractants. This difference stayed stable over months of testing, suggesting it’s a deep feature of skin chemistry rather than something you can easily change.

At the receptor level, specific ionotropic receptors on mosquito antennae and legs are tuned to detect these fatty acids. Receptors like IR75k1 and IR75k3 in Aedes aegypti respond to nonanoic and octanoic acids at levels roughly ten times greater than to any other odor blend tested.⁶ Even when researchers knocked out the co-receptors these systems depend on, mutant mosquitoes could still tell highly attractive people apart from less attractive ones, hinting that there are redundant sensory pathways backing up the system.⁷

Lactic acid is another major player. Humans carry uniquely high levels of L-lactic acid on their skin compared to other animals, and this is part of why certain mosquito species evolved to specialize in biting us. L-lactic acid on its own doesn’t draw mosquitoes in, but it dramatically amplifies the attractiveness of other skin odors and carbon dioxide. Researchers found they could make one of a person’s index fingers more attractive than the other simply by adding lactic acid to the airstream around it, within the natural range of variation that a human hand already produces.⁸ Combined with another skin compound called 2-ketoglutaric acid, lactic acid triggers the full sequence of host-seeking behavior in Aedes aegypti, from takeoff to upwind flight to landing.⁹

Your Skin Bacteria Are Part of the Signal

The volatile compounds that attract mosquitoes don’t all come directly from your sweat glands. Many are produced by the bacteria living on your skin, which metabolize sweat components into airborne chemicals. Research comparing highly attractive and poorly attractive people found clear differences in skin microbiome composition. Staphylococcus bacteria were about 2.6 times more abundant on people who attracted more mosquitoes, while Pseudomonas bacteria were about 3 times more abundant on people mosquitoes tended to avoid.¹⁰

Counterintuitively, having a more diverse bacterial community on your skin was associated with being less attractive to mosquitoes. People who were rarely bitten had bacterial diversity scores about 38% higher than those who were frequently targeted. A follow-up study confirmed these patterns and found specific bacterial types associated with volatile compounds already known to attract Anopheles mosquitoes.¹¹ This may help explain why mosquitoes seem especially fond of feet and ankles, where bacterial communities are particularly dense and distinct.

How Mosquitoes Find You in the First Place

Blood type and skin chemistry only matter once a mosquito is close enough to detect them. The hunt actually begins at a distance, driven by carbon dioxide. Female Anopheles gambiae mosquitoes become activated and fly upwind at CO2 concentrations as low as 0.01% above background levels, a threshold so sensitive it can detect a single human breath diluted across a large room.¹² This is why larger people, pregnant women, and anyone breathing harder after exercise tend to attract more mosquitoes: they produce more CO2.

But CO2 is really just the long-range alarm bell. Once a mosquito gets close enough to see and smell a potential host, the other senses take over. Research on Aedes aegypti shows that once a female arrives near a person, she stops orienting to CO2 and switches to navigating by the suite of odors from human skin.¹³ Body heat then provides the final targeting cue. Mosquitoes have thermal sensors on their legs that guide them to land on warm skin, and these sensors are so important that when researchers disabled the main olfactory receptor in mosquitoes, the insects compensated by becoming even more sensitive to heat. A receptor called Ir140, normally expressed at low levels in the legs, ramped up its activity to fill the gap.¹⁴

Color vision adds yet another layer. After being activated by CO2, mosquitoes become strongly attracted to long-wavelength colors, particularly orange and red, which happen to dominate the visible spectrum of human skin regardless of skin tone. They show little interest in these colors until they’ve first smelled CO2, suggesting that odor “unlocks” their visual search.¹⁵

The Genetic Lottery of Mosquito Attraction

If it seems like some people are just born to be mosquito magnets, there is real evidence for that. A twin study found that identical twins showed highly correlated attractiveness to mosquitoes, while non-identical twins did not. The estimated heritability of mosquito attraction was around 0.62, meaning roughly 62% of the variation in how attractive people are to mosquitoes can be attributed to genetic factors.¹⁶ A separate twin study in Australian adolescents also found a strong genetic influence on frequency of being bitten, with no significant differences between males and females.¹⁷

Blood type is one genetically determined trait that could contribute to this heritability. But it’s just one piece among many. The genes controlling your skin’s fatty acid profile, the composition of your sweat, and even which bacteria your skin tends to harbor are all heritable traits. Together, they create the overall “scent fingerprint” that makes one person a mosquito buffet and another person relatively invisible. If your parent was always the one getting bitten at backyard barbecues, you’ve likely inherited at least some of that chemical profile.

Alcohol, Bananas, Garlic, and Other Myths

One lifestyle factor with real experimental backing is alcohol consumption. A study found that the percentage of mosquito landings on volunteers increased significantly after drinking beer compared to before drinking. Curiously, the researchers found no correlation between the increased biting and either ethanol in sweat or skin temperature, leaving the actual mechanism unclear. Something about drinking changes your scent profile in a way mosquitoes notice, but scientists haven’t pinpointed what that change is.¹⁸

Other supposed dietary protections don’t hold up at all. Garlic pills and vitamin B12 supplements are commonly recommended as natural mosquito repellents, but controlled tests found no impact on mosquito biting or landing rates.¹⁹ The garlic myth in particular has been around for decades and refuses to die despite repeated failures in testing. No food, supplement, or vitamin has been reliably shown to make you less attractive to mosquitoes.

What Happens After the Bite Depends on Blood Type Too

Even if the question of which blood type mosquitoes prefer remains unsettled, there is a separate and surprisingly clear finding: the blood type a female mosquito feeds on affects how many offspring she produces and how healthy those offspring are. When Anopheles stephensi females were fed type B blood, they laid an average of about 216 eggs per female, compared with roughly 98 for type O and just 65 for type A. Fertility rates followed a similar pattern, with type B blood yielding the highest success at around 92% and type A the lowest at about 60%.³

For Aedes aegypti, the dengue vector, a laboratory study found that blood groups B-negative and O-negative produced the highest fecundity, with significantly larger eggs and greater egg viability. Offspring from these blood groups also developed into larger larvae with wider head capsules, suggesting better overall fitness. In contrast, B-positive and AB-positive blood resulted in the lowest reproductive success.²⁰ These are lab findings using membrane feeders, not free-flying mosquitoes choosing human hosts, so they don’t tell us about preference. But they raise an intriguing evolutionary question: if feeding on certain blood types produces more and healthier offspring, natural selection might gradually push mosquito populations toward preferring those blood types.

Practical Takeaways for Avoiding Bites

You can’t change your blood type, your genetics, or your skin’s carboxylic acid output. So what can you actually control? The factors most within your power are the ones that amplify the signals mosquitoes already detect. Exercising raises your CO2 output, body heat, and lactic acid production simultaneously, which is why mosquitoes swarm after a jog. Showering after exercise removes some of that chemical attractant buildup, though it won’t change your baseline skin chemistry. Wearing light-colored clothing may help marginally since mosquitoes are drawn to longer-wavelength colors like red and orange after they’ve been activated by CO2. Drinking alcohol appears to boost your attractiveness for reasons nobody fully understands, so staying sober outdoors at dusk won’t hurt.

Beyond behavior, proven repellents containing DEET, picaridin, or oil of lemon eucalyptus work by interfering with the mosquito’s ability to detect and follow your scent plume. These remain far more effective than any dietary change, supplement, or blood-type workaround. The next time someone tells you mosquitoes prefer type O blood, the accurate response is that one species in one study showed a modest preference, two other species preferred type B, and in all cases the chemical landscape of your individual skin matters far more than the letter on your blood donor card.