The Truth About Why Mosquitoes Love You

Backyard barbecues, picnics, outdoor concerts, and poolside evenings — they all have one thing in common and it's not summer fun and fond memories. Nope. It's mosquitoes. Those flying, buzzing, blood-sucking harbingers of itchiness.

Perhaps you can't relate. Maybe you're that annoying person who stands around at parties in shorts and a tank top making casual remarks about how mosquitoes don't bother you. How lovely for you. It's irritatingly true that some people seem to be blessed with natural mosquito repellent qualities. Others aren't that lucky — they can slather on the DEET, dress in long sleeves and jeans, and still walk away with millions of itchy welts.

Fortunately for Americans, mosquitoes are mostly just annoying (though not always). In other parts of the world, mosquitoes can be deadly — and that's why science is working to understand just what it is about some people that makes them especially attractive to mosquitoes. And though many of the biological and chemical pieces of the puzzle are still a mystery, here are some of the things scientists do know, or suspect, so far.

So biologically, what is it about high attractor types that have doomed them to always being the most popular hors d'oeuvre at the mosquito buffet? As it turns out, a person's deliciousness is a complicated mix of varying components, much like the deliciousness of the cheese appetizer is a complicated mix of cheddar, gouda, gorgonzola, and romano.

According to a 2011 study published in the journal PLOS One, the composition of a person's skin microbiota can have a lot to do with his or her deliciousness. The study found that the microbial communities that live on a person's skin can impact the way that person smells to a mosquito — you know, like the smell of a nice aged gouda vs. the smell of whatever that thing in Jell-O is. People who had "a higher abundance, but lower diversity" of skin bacteria tended to be more attractive to mosquitoes, so if you have a lot of one type of bacteria crawling all over you and not much variety in the types of bacteria that are crawling all over you, mosquitoes are more likely to go for you.

You're probably still getting over the whole "microbial communities are crawling all over me" thing, but the takeaway from all this is that your skin gives off an odor and that odor can change depending on how many microbes inhabit your skin, and that's one part of what brings the mosquitoes to the buffet.

Let's say you're tired of single-handedly sustaining your town's mosquito infestation, so you decide to drop $7.99 on a bottle of bug spray. Cool. You slather yourself with the greasy, smelly stuff, resolve to take four or five baths at the end of the day to wash it all off and, feeling armed and confident if not especially attractive to other human beings, you arrive at the summer barbecue. And then you get eaten by mosquitoes anyway.

What happened? Well according to Smithsonian, mosquitoes are a bit like bacteria in that they develop resistance to insect repellent. And in the mosquitoes' case, it's not just a resistance that happens over generations, it's a resistance that happens over a matter of hours. In 2013, researchers at the London School of Hygiene and Tropical Medicine exposed Aedes aegypti mosquitoes to DEET, the most commonly used insect repelling chemical, and learned that it took just three hours for about half the mosquitoes to stop caring about DEET. In other words, the bugs acclimated, ignored the smell, and tried to eat the people who were slathered in the stuff anyway.

This isn't exactly a recommendation for you to avoid bug spray before attending an outdoor party in the summertime, though. A few hours of freedom is still way better than the alternative, for many people.

So you can use bug spray, avoid alcohol, lose weight (without gaining too much muscle), and scrub yourself with antibacterial soap to get all those microbial cities down to manageable villages (although probably don't do that because of superbugs and bacterial resistance and so on). You cannot, however, change your blood type.

Some studies have found that mosquitoes favor people with a particular blood type. And as it turns out, the blood type that's most attractive to mosquitoes is type O, which is the most common blood type there is. Roughly 38% of Americans are O-positive, while another 7% are O-negative. In a 2004 study by the Institute of Pest Control Technology, researchers discovered that the mean relative percent landing of mosquitoes on people with type O blood was about 83.3%, compared with 46.5% for people with A blood types (who account for about 40% of the American population overall). So you're about twice as likely to become mosquito food if you're type O than you are if you're type A, although that number isn't especially meaningful unless there are only a few mosquitoes in the room. A 46.5% landing rate really just means you won't be bitten as much, not that you won't be bitten at all.

Incidentally, not everyone thinks the blood type thing is a fact, but either way you're still going to need to bring the DEET and avoid the beer. Sorry.

Some people run hotter than others. In fact, normal human adults can have temperatures that vary between 97.8 degrees and 99 degrees Fahrenheit. So if you often run at the higher end of that range, you're probably more of a target for mosquitoes. Likewise, when you work out your metabolism speeds up and your core temperature rises, plus you become sweaty, plus you have that lean muscle mass thing working against you, so becoming a couch potato is really starting to sound like a good idea. As a bonus, you'll save on the gym membership fees, although you'll probably lose on pay-per-view fees and long-term health care so financially it may be kind of a wash.

Anyway, for mosquitoes, heat is probably a useful way of determining how easy it will be to get blood out of you. "[Mosquitoes] use heat to very quickly to determine where blood is closest to the surface," medical entomologist Jonathan Day told ABC News. And when you've been exercising or are just hot and sweaty in general, your blood is closer to the surface of your skin. So it's kind of like if you set up a buffet table where there are some appetizers in the middle and some around the edges — most people are going to go for the stuff that's easier to get to. Unless it's cheese-stuffed with extra cheese and cheese sauce. And bacon. Then, who cares how many other bowls and trays you have to reach over, right?

Many mosquitoes are vegetarians. Wait, what? It's true — according to Discover, male mosquitoes drink nectar and plant juices and probably spend their free time lecturing others about the health benefits of kale and kombucha. It's only the female mosquitoes that drink blood, and they only do it because they need the protein to make their eggs.

So the female mosquito's affinity for pregnant women is sort of serendipitous, really — she's just a being trying to become a mother, so surely all those mothers to be out there can spare a tiny little bit of blood? Suuure. But whether pregnant women like it or not, they're mosquito magnets, and it's not just because pregnant women emit about 21% more carbon dioxide than non-pregnant humans do. It's also because pregnant women tend to have higher body temperatures. The authors of a 2000 study on mosquito attractiveness in pregnant women in Gambia also found that behavioral changes could account for pregnant women getting bitten more often — partly because pregnant women are constantly having to pee, which in Gambia usually means leaving the protection of mosquito netting to go outdoors. That's not so much of a problem for American women, but if you find yourself leaving the safety of your house because of an insatiable craving for barbecued hotdogs, well, make sure to dress in neutrals, loose, long sleeves, and baggy pants. Just so you know, mosquitoes can still bite you through snuggly-fitting clothes.

You might have met vegans who swear their animal-free diet helps protect them from mosquitoes, which is handy for them because many of them also won't swat a mosquito on principle. But so far science hasn't really been able to confirm whether or not your diet has anything to do with how mosquito-attractive you are.

According to the New York Times, scientists at the University of Connecticut Health Center tested the garlic-as-mosquito-repellent theory in 2005 and concluded that there didn't seem to be any benefit to eating loads of garlic, unless what you really want is to repel other humans. Subjects were asked to alternate between eating large quantities of garlic some days and placebo on others, and then they were offered up as snacks to swarms of mosquitoes, which sounds like the most fun research project ever. Sadly, the subjects were bitten just as often on the garlic-eating days as on the non-garlic eating days, so the only potential benefit was that vampires probably left them alone, though that's a much more difficult thing for scientists to measure.

Anyway, the New York Times went on to say that there really hadn't been any other studies that pegged any sorts of food or special diets as mosquito-repelling, so there's still only one way to keep from being bitten — stay indoors and be a couch potato. Tip: Game of Thrones was pretty good right up until the last couple episodes.