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.

You might be delicious to mosquitoes

When you go to a buffet, you've got lots of choices. There's the liver pate, the raw oysters, that weird thing entombed in Jell-O, and the bacon-wrapped, cheese-stuffed, baked cheese bites with extra cheese and a cheese dipping sauce. Which one do you go for? Well, unless you have a thing for liver pate and raw oysters or weird things in Jell-O, you go for the cheese because cheese is delicious and those other things are less delicious. Therefore it should not surprise you to hear that mosquitoes also prefer delicious things over less-delicious things. And if you're the person who always gets eaten alive at outdoor summer barbecues, well, it might be because you are delicious.

According to NBC, studies suggest that around 20% of the human population qualifies as "high attractor types," which sounds awesome if it means you're highly attractive to, say, other human beings. But no, no, being a "high attractor type" means that mosquitoes would rather eat you than the liver pate or the raw oysters.

So that sucks, but is there anything you can do to make yourself less appealing to mosquitoes? Yes. At the next barbecue, you can sit next to someone who the mosquitoes like even more than they like you. Or you can wear insect repellent, or long sleeves and a turtleneck. Or you can not go to summer barbecues. That last one is really the only guarantee.

Besides being gross, all that bacteria crawling around on you might attract mosquitoes

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.

The more carbon dioxide you produce, the yummier you seem to mosquitoes

There are other factors at play, too, and one of the most important is the amount of carbon dioxide you emit. According to NBC News, carbon dioxide is the mosquito's primary attractor — in fact, they have a sensory mouth appendage called a "maxillary palp" that basically acts as a carbon dioxide detector, thus notifying them when and where the party will be. Sort of like an evite app for mosquitoes.

It's not because they're after the CO2, though, it's just that the presence of CO2 means the presence of bodies. And the more CO2 there is coming out of an individual body, the more attractive it is to the mosquitoes.

People who have higher metabolic rates exhale more carbon dioxide. Loosely translated, that means that people who exercise more and have more lean muscle mass are going to be bitten more often. So if you ever needed a reason to avoid the gym, well, there you go. Except that larger people also produce more carbon dioxide, so if you ever needed a reason to go to the gym and lose those extra pounds, well, there you go. Pregnant women also produce more carbon dioxide, so if you ever needed a reason to not have children, well ... also, children become teenagers and grow up to hate you, so there's another reason. If you're lucky, though, they will inherit your mosquito super-attractiveness and you'll have your revenge.

No worries, just put on your mosquito repellent

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.

It's okay, just stop drinking beer

Prepare yourself because this is the suckiest piece of information you're likely to hear today. Mosquitoes are more likely to bite you if you drink beer. Yes, it's true, much like other human beings become more attractive to you when you drink beer, mosquitoes are more attracted to you when you drink beer.

According to a 2002 study published in PubMed, after volunteers drank just 350 ml of beer (that's the equivalent of a single bottle) they became "significantly" more attractive to mosquitoes. "Our study demonstrated that percent mosquito landing on volunteers significantly increased after beer ingestion compared with before ingestion, showing clearly that drinking alcohol stimulates mosquito attraction," concluded the study's authors. So feel free to continue attending those summer barbecues. Just make sure you have poor muscle mass, slather yourself in smelly bug spray that only sort of works, and say "no thanks" to the alcohol. And have fun.

Do you have the most common blood type known to humans?

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.

Mosquitoes like your stink

So bad news for people who work out — as it turns out, it isn't just your muscle mass (and hence elevated carbon dioxide production) that affects how much mosquitoes like you, it's also your sweat. According to Self Magazine, sweaty people are more attractive to mosquitoes than not-sweaty people, which is one specific thing that differs from what people tend to find attractive in other people.

Entomologist Whitney Qualls told Self that mosquitoes like lactic acid, which is a chemical commonly found in stinky armpits. They also like uric acid and ammonia, two chemicals that are produced by that microbial community that lives on your skin. (Let's just call those chemicals "bacterial emissions.") But it's not necessarily just the stuff your body and its entire metropolis of alien organisms produces; it's also the stuff you deliberately put on your body, like perfumes and colognes. Sweet-smelling perfumes may act as mosquito attractants, though never fear — some perfumes, like some made by Victoria's Secret, have actually been shown to repel mosquitoes. So hey, just drop $58 on 1.7 fluid ounces of that stuff and maybe you'll be mosquito-free for at least the three hours that it probably takes for them to decide they don't really care about your Victoria's Secret perfume anymore. Hint: DEET might not smell as good but it's way, way cheaper.

Mosquitoes like people who run hot

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?

Your clothes may be saying, "come hither, mosquitoes"

The way you dress makes a big difference in a lot of aspects of your life. It can make you appear more suitable for a job. It can make you more attractive to other humans. It can make you cooler or warmer or sweaty or freezing to death. It can make you gothic or annoyingly peppy. It can also make you more attractive to mosquitoes.

According to the Telegraph, in August 2010 women in Thailand were warned against wearing the black leggings that were fashionable at the time because black was thought to attract dengue fever-carrying mosquitoes. But how much truth was there to that?

Probably a lot, actually. It's not really because mosquitoes like certain colors, though — it's because some colors just make you more visible to mosquitoes than others. So light colors, especially light neutrals like white, khaki, and beige tend to have a sort of camouflage effect, while dark colors or bright colors may have an attractive effect. So now, you not only have to slather yourself in smelly bug spray and say no to the beer, you also have to dress boringly. It's gonna be a fun summer.

Mosquitoes like pregnant women

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 just be more sensitive to mosquito bites

Just because you suffer when mosquitoes bite you doesn't necessarily mean you're more prone to being bitten. Some people may just have more severe reactions to mosquito bites, and that can create the illusion of deliciousness. "The actual bite of the mosquitoes can be innocuous," dermatologist Gary Goldenberg told Self. "Most people produce an allergic reaction to mosquitoes by releasing histamine — a chemical that causes itching and hives." But some people don't produce as much histamine as others, and a lesser reaction to mosquito bites might lead those people to conclude that mosquitoes just don't bite them very often.

It's important to keep in mind that you might think you aren't being bitten, but that doesn't definitively mean you aren't being bitten. So it's important to put bug spray on anyway, especially if you're in a place where mosquito-borne illnesses are common. (And that's not just non-U.S. countries, either — West Nile virus and dengue fever are two mosquito-borne illnesses that occur in the United States, and Zika virus has been locally transmitted in Florida and Texas.) So just because a mosquito bite didn't swell up and itch doesn't mean it can't make you sick. Wear bug spray whether you think you're mosquito-delicious or not.

You probably can't repel mosquitoes by changing your diet

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.