There is always one. That person who, no matter what, always
comes back from spending a warm summer evening sitting outside covered
in mosquito bites.
While there is some evidence to suggest that people are really bad at
knowing whether or not they are the unlucky ones, there are things that
can increase your likelihood of getting bitten. Although there is lots
of anecdotal evidence from people about what influences the little
critters to bite, from eating garlic to having “sweet” blood, there are
some aspects that have been proven by science to genuinely increase your
chances.
Unfortunately, not all of the causes are something you can actually
do something about. Take blood type, for example. One study has found
that while those who have blood type O coursing through their veins are
more likely to get a less than friendly visit from a mosquito than other
blood types, they’re only more attractive to the insects when compared
with those with blood type A. They found that a particular sugar found
in blood type O was attractive to the mosquitoes, though once a mosquito
has picked its target, it’s unlikely blood type will make much
difference.
Carbon Dioxide
Another thing that we all have to do is breathe, and this isn’t great
if you’re trying to avoid the pesky little biters. When homing in on
their target, all mosquito species will use something called a maxillary
palp to sense the carbon dioxide you’re exhaling. Mixed with the host’s
body odor and both molecules have been found to induce a take-off and
sustained flight of the insects. It is for this reason that people who
breathe out more, including larger people and adults, tend to get bitten
more than those who exhale less.
Lactic acid
The pesky little insects are not only searching for carbon dioxide,
they are also on the lookout for other markers too. One of these, it
seems, is lactic acid. Research has shown that yellow fever mosquitoes
are significantly more attracted to those who have more lactic acid on
their skin, even making those who were less “attractive” to the insects
more attractive. This, in addition to an increase in body temperature,
could go some way to help explain why those who have just exercised seem
more likely to get bitten.
Pregnancy
The previous cause could also be related to why it seems that
pregnant women are more likely to receive itchy red bites. One
study found that women in the late stages of pregnancy exhaled 21
percent more breath – including that crucial carbon dioxide – when
compared to non-pregnant women. Another reason could be related to the
fact that pregnancy increases blood flow to the skin, which means that
on average they run at around 0.7°C warmer than normal, making them
easier for heat-seeking insects to find.
Beer
This one is a little contentious. While a study has previously found
that by drinking as little as 350ml of 5.5 percent beer the number of
mosquitos on the volunteer’s skin significantly increased, it was only a
very limited study of 13 people. Not only that, but it doesn’t
necessarily mean that the insects then went on to feed on them, and the
researchers even go on to say that they found no correlation between the
amount on ethanol detected in the sweat and the amount of beer actually
consumed. So while it could be a factor, it is a far from settled
matter.

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