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Do Mosquitoes Bite Some People More Than Others?

How do blood type, exercise habits, and even pregnancy factor into whether or not mosquitoes find someone irresistible?

By
Sabrina Stierwalt, PhD,
Episode #303

This episode is dedicated to my neighbor Todd. Whenever we are outside hanging out in the evening, and the sun starts to set and the mosquitoes begin to appear, I know that he will act as cover. I’ll escape with only a few or often no bites at all, while he, unfortunately, will end up coated in them.

Todd is not alone. Scientists estimate that 20% of people are more likely to attract mosquitoes and thus get bitten more often. But what makes some people more delicious (to mosquitoes) than others?

What Attracts Mosquitoes to Some People More than Others?

Whether or not we are doomed to be highly attractive to mosquitoes is mostly determined by our genetics. For starters, the main way mosquitoes search for their next victim is by tracking down our carbon dioxide output, a telltale sign of a mammal’s existence. This means your metabolic rate, or the amount of CO2 your body releases as it burns energy, is a big factor when it comes to attracting mosquitoes.

To a large extent our metabolism is predetermined by our genetics but we do have the power to alter it somewhat. Drinking alcohol and exercising can both raise your resting metabolic rate and thus make you more attractive to mosquitoes. So going for a run and then stopping to have a beer at dusk is just asking to get bitten.

Mosquitoes also prefer pregnant women, a fitting prey since only female mosquitoes bite at all out of a need to develop fertile eggs. Pregnant women on average have higher metabolic rates than nonpregnant women. One study found pregnant women exhale 21% more CO2 than their nonpregnant counterparts. Pregnant women are also at another disadvantage: their body temperatures tend to be higher, another mosquito attractor.

We also naturally emit varying levels of acids and chemical signatures in our skin, some of which are used by mosquitoes to track down their next meal. Mosquitoes sniff out humans via the lactic acid, uric acid, and ammonia on their skin, byproducts expelled through our sweat (and thus another reason exercising can bring on the bugs). Some studies also suggest that people with higher levels of steroids or cholesterol on their skin attract more mosquitoes. This does not mean that someone with higher cholesterol will be more of a mosquito magnet, but that those people who are better at processing cholesterol so that more of it is left over to remain on the skin will instead attract more of the insects.  

Of course, chemical attraction likely varies a bit depending on the species of mosquito, but given the large impact mosquito-borne diseases have in certain populations, what chemical signatures attract, or deter, mosquitoes is an active and important area of scientific research.

Do Mosquitoes Prefer a Certain Blood Type?

Perhaps not surprisingly, mosquitoes also prefer certain blood types over others. One study found that those with type O blood were twice as attractive as those with type A blood. Those people with type B and type AB blood fell somewhere in between.

However, not everyone secretes a chemical signal that reveals what our blood type is—15% do not—and mosquitoes prefer a person who does send out that chemical message no matter what their blood type over someone that does not.

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