Only female mosquitoes bite, and they do it for one reason: they need the nutrients in your blood to produce eggs. Both male and female mosquitoes feed on plant nectar for energy, but nectar alone doesn’t contain enough amino acids for a female to develop a viable batch of eggs. Your blood supplies those amino acids, particularly as building blocks for the yolk proteins that nourish developing mosquito larvae.
Why Blood Matters for Egg Production
When a female mosquito takes a blood meal, her body breaks down the proteins into individual amino acids and routes them to her ovaries. Some amino acids are concentrated well beyond their original levels in the blood itself. Tyrosine, for instance, accumulates in the ovaries at 1.7 times its concentration in the blood meal. These amino acids serve a dual role: they act as signaling molecules that trigger egg maturation, and they become the physical raw material for yolk proteins. Without a blood meal, most mosquito species simply cannot reproduce. Males never bite because they play no role in egg development.
How Mosquitoes Find You
A mosquito doesn’t just stumble onto you. It follows a sequence of cues that narrow your location from dozens of feet away down to the exact spot on your skin where it lands.
The first signal is carbon dioxide. Every time you exhale, you release a plume of CO2 that mosquitoes can detect from more than 30 feet away. They have dedicated smell receptors on their antennae, near their mouths, and on the tube-like proboscis they use to feed. Once a mosquito locks onto a CO2 trail, it flies upwind toward the source.
As it gets closer, your body heat and the moisture radiating off your skin take over as guides. Mosquitoes can sense the slight warmth surrounding a person and use it to zero in on exposed skin. At the final stage, within inches, they respond to the chemical cocktail rising off your skin’s surface.
Your Skin Bacteria Create Your Scent Profile
The bacteria living on your skin are responsible for most of the scent that attracts mosquitoes. These microbes feed on compounds in your sweat and release small volatile molecules as byproducts, including lactic acid, acetic acid, and ammonia. Lactic acid is the single most well-documented mosquito attractant produced by human skin, and the bacteria that generate the most of it belong to a group called Staphylococci.
These skin odors don’t work alone. Lactic acid acts as a kind of gatekeeper: in lab studies, mosquitoes ignored other skin scents like acetic acid and octanal unless lactic acid was also present. The combination of lactic acid, ammonia, and CO2 together is what triggers both the approach flight and the decision to land. This means your unique mix of skin bacteria, and how much lactic acid they produce, plays a large role in whether mosquitoes single you out in a crowd.
Why Some People Get Bitten More
If you feel like mosquitoes target you specifically, you’re probably right. A twin study published in PLOS One found that attractiveness to mosquitoes has a heritability of about 62%, putting it in the same range as traits like height and IQ. Identical twins showed much more similar bite rates than fraternal twins, suggesting that your genes influence the composition of your skin chemicals and microbiome in ways that make you more or less appealing.
Pregnancy is another major factor. Pregnant women are roughly twice as attractive to mosquitoes as non-pregnant women, based on research published in The Lancet. Two physiological changes drive this: women in late pregnancy exhale about 21% more air (and therefore more CO2), and their abdominal skin temperature runs about 0.7°C higher. Both signals make them easier for mosquitoes to detect.
You may have heard that blood type matters, with type O supposedly drawing more bites. The evidence here is shaky. One 2019 study found a dengue-carrying mosquito species preferred people with type O blood, but other research has failed to replicate this consistently. The current scientific consensus leans toward skin odor and microbiome composition as far stronger predictors than blood type.
Diet, Beer, and Bananas
Folk remedies suggesting that eating garlic or taking vitamin B will repel mosquitoes have been tested in controlled studies. Neither garlic pills nor vitamin B12 had any measurable effect on biting or landing rates.
Beer, on the other hand, does make you more attractive to mosquitoes. It’s the one dietary component with clear, replicated evidence linking consumption to increased mosquito interest. The mechanism isn’t fully understood, but it likely involves changes to your skin’s volatile emissions after drinking.
Bananas are a more surprising finding. Two species of malaria-carrying mosquitoes showed significantly increased attraction to human hand odors about an hour after subjects ate a banana. The effect varied between individuals, with some people showing no change, but the overall trend was strong enough to lend support to what had previously been dismissed as internet folklore.
What You Wear Matters
Mosquitoes use visual cues alongside chemical ones, and color makes a difference. In field studies, host-seeking mosquitoes were significantly more attracted to black targets than to white ones. This held true for several major species, including the mosquito that spreads dengue. Striped patterns also drew more landings than solid white for daytime-biting species. The takeaway is simple: light-colored clothing is consistently the least attractive to mosquitoes.
Reducing Your Exposure
The CDC recommends insect repellents registered with the Environmental Protection Agency. The most widely available active ingredients are DEET, picaridin, IR3535, and oil of lemon eucalyptus. All are proven safe and effective when used as directed, including for pregnant and breastfeeding women. Oil of lemon eucalyptus should not be used on children under 3. If you’re also wearing sunscreen, apply the sunscreen first and the repellent on top.
Beyond repellent, wearing light-colored, long-sleeved clothing reduces the visual and thermal cues mosquitoes rely on. Since skin bacteria drive so much of your scent profile, showering before spending time outdoors can temporarily lower the concentration of attractant chemicals on your skin, though the effect fades as bacteria repopulate. Exercising outdoors increases your CO2 output, body heat, and lactic acid production simultaneously, which is why mosquitoes tend to swarm people mid-workout.