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.
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.
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.
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.
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.