Mosquitoes show a measurable preference for type O blood. In controlled experiments, people with type O blood received about 83% of mosquito landings, compared to roughly 47% for type A. But blood type is only one piece of a larger puzzle. Your skin chemistry, body heat, the carbon dioxide you exhale, and even whether you’re pregnant all play significant roles in how irresistible you are to mosquitoes.
What the Research Shows About Blood Type
A well-known study published in the Journal of Medical Entomology tested 64 volunteers across all four ABO blood groups. The results showed a clear hierarchy: type O drew the most landings (78.5%), followed by type B (56.9%), type AB (48.0%), and type A (45.3%). The difference between type O and type A was statistically significant, meaning it wasn’t likely due to chance.
There’s an important wrinkle here, though. About 80% of people are “secretors,” meaning they release chemical markers of their blood type through their skin and in bodily fluids like sweat and saliva. Among secretors, the gap widened further: type O secretors attracted landings 83.3% of the time, versus 46.5% for type A secretors. If you’re a type O secretor, you’re essentially broadcasting your blood type to every mosquito nearby. Non-secretors of any blood type were generally less attractive.
Not All Mosquito Species Agree
Here’s where it gets more complicated. The preference for type O blood has been documented mainly in certain mosquito species, particularly Aedes albopictus (the Asian tiger mosquito) and Aedes aegypti (the yellow fever mosquito). Other species have different tastes entirely.
A study on Anopheles stephensi, an important malaria-carrying mosquito, found the opposite pattern. Out of 450 blood-fed mosquitoes, 40% had fed on type AB blood, 24% on type A, 21% on type B, and just 15% on type O. That’s a near-reversal of the Aedes results. Older research on Anopheles gambiae, the primary malaria vector in Africa, also showed some preference for type O, but the picture across species is inconsistent. The mosquito biting you in your backyard may not have the same preferences as one in a research lab halfway around the world.
Why Skin Chemistry Matters More
Blood type influences mosquito attraction, but your skin’s unique chemical signature likely matters more on a day-to-day basis. Research supported by the National Institutes of Health found that people who were most attractive to mosquitoes had significantly higher levels of carboxylic acids, a type of fatty acid, on their skin. These compounds are produced partly by the hundreds of bacterial species living on your skin surface, and the specific blend varies from person to person.
The most striking finding: these chemical profiles stayed stable over time. People who were mosquito magnets remained mosquito magnets for years. The researchers couldn’t confirm that carboxylic acids were directly driving the preference, but the association was strong and consistent. This helps explain why two people with the same blood type can have wildly different experiences at a summer barbecue.
Other Factors That Attract Mosquitoes
Beyond blood type and skin chemistry, several other traits make you a bigger target:
- Carbon dioxide output. Mosquitoes detect CO2 from up to 50 meters away. Larger people and those exercising exhale more of it, which is partly why adults get bitten more than children.
- Body heat. Higher metabolic rates and physical activity raise your skin temperature, making you easier for mosquitoes to locate at close range.
- Pregnancy. Pregnant women attract roughly twice as many mosquitoes as non-pregnant women. In one study, the number of mosquitoes entering bednets was 1.7 to 4.5 times higher around pregnant women, and they received 70% of bites compared to 52% for non-pregnant women. The likely drivers are increased body temperature and higher CO2 output during pregnancy.
- Sweat and lactic acid. Fresh sweat contains lactic acid and ammonia, both of which mosquitoes find appealing. Exercise makes you a target on multiple fronts: more CO2, more heat, more sweat.
- Dark clothing. Mosquitoes use visual cues alongside chemical ones. Dark colors like black, navy, and red are easier for them to spot against most backgrounds.
What You Can Actually Do About It
You can’t change your blood type or your skin microbiome, but effective repellents work regardless of how attractive you are to mosquitoes. The EPA registers several active ingredients for skin-applied repellents. DEET remains the most widely studied and is effective for hours per application. Picaridin offers similar protection with a lighter feel on the skin. Oil of lemon eucalyptus is the most effective plant-derived option. IR3535 and 2-undecanone are additional alternatives for people who prefer to avoid DEET.
Wearing light-colored, loose-fitting clothing that covers your arms and legs reduces the amount of skin available for landing. Mosquitoes are weak fliers, so a simple fan on a porch or patio can make a noticeable difference. Eliminating standing water around your home, even in small containers like plant saucers and clogged gutters, removes breeding sites within biting range of your yard.
If you’re type O and feel like you always get bitten more than everyone around you, the science suggests you’re not imagining it. But the gap between “most attractive” and “least attractive” people has far more to do with overall body chemistry than blood type alone. Two type O individuals can have very different experiences depending on their skin bacteria, activity level, and what they’re wearing.