Practice English Speaking&Listening with: 5 Things That Make You a Mosquito Magnet

Difficulty: 0

This episode of SciShow is supported by Brilliant. You can learn more at

[ ♪INTRO ]

Ah, summer.

Time to head outside for a hike, or a trip to the lake, or maybe host a barbecue.

But, no matter where you go, youll probably get some unwanted attention from a certain

flying blood-sucker.

Thats right.

Its summer.

Its mosquito season, in the northern hemisphere anyways .

And every year it seems like theres that one person who gets the lions share of the bites.

And that person is always me.

And always on my right leg for some reason.

Were not going to get into the leg specificity today, but there are some theories about why

some people are mosquito magnets, a few of them actually have some scientific backing.

And, spoiler alert, it isnt one single trait, because mosquitoes dont use one

single cue to find their meals.

So, here are five things that might be making you a mosquito magnetand what, if anything,

you can do to lessen your appeal.

Now, youve probably heard that mosquitoes find their human targets by our exhaled breaths

and thats true, but theres even more to it than that.

What theyre attracted to isnt that lingering tuna sandwich you ate earlier but rather the

carbon dioxide you breathe out, thats part of your normal metabolism.

Scientists think that there are two ways CO2 increases your odds of getting bit.

One, itactivatesthe mosquitomeaning it triggers them to fly, and to fly more quickly.

And two, its an attractant.

Scientists think they use it to it orient themselves to the source of the gas with the

help of air currentsthough they only seem to do this when its released in bursts.

Carbon dioxide is such a big part of how mosquitoes find their targets that they have three types

of smell-sensing cells in their mouth parts that can detect it.

Theyre called Gr1, Gr2 and Gr3.

In a 2014 study published in the journal Cell, scientists showed just how important these

cells are by creating genetically modified Aedes aegypti mosquitoes whose Gr3 sensory

cells didnt work.

Those modified mosquitoes no longer got all excited when CO2 was puffed into the air.

And, they were about 15% worse than their unmodified relatives at hunting out a person

in a large, enclosed area.

But whats even more interesting was that the mosquitoes lacking their Gr3 cells were

also no longer attracted to other cues that help them find hosts.

That suggested that carbon dioxide might actually have a third role as a gatekeeper of sorts

for other attractants.

And that makes sense, because its a pretty good indicator of animal life.

So, if you dont want to get bit, you could just stop breathing all the time.

Easy peasy.

Except...the mosquitoes lacking the Gr3 sensor could still find a target at close range.

And that suggests CO2 draws the insects in from a distancewhile something else helps

them zero in when they get close to their target.

And obviously, I was joking about the whole not breathing, but while you can never emit

zero carbon dioxide, things that make you breathe more or more deeply could increase

your attractiveness to mosquitoes, things like, for example pregnancy.

Because of course you need to attract more mosquitoes on top of everything else youre

dealing with when theres a fetus growing inside you.

And this also applies to exercise, which causes you to breathe out more CO2.

So you might come home with a few more bites after a run than if you just went for a walk.

Speaking of running, that nice glistening sweat you produce when exercising can also

draw mosquitoes in.

Although moisture is an attractant for them, what theyre mostly sensing is how you smell.

Many of the chemicals in your sweat are considered volatile compounds, meaning they can easily

turn into a vapor.

This includes things like lactic acid, amines, sulfides, and carboxylic acids.

And most of these are formed by the communities of bacteria that live on your skin.

So part of the mosquito magnet equation has to do with these bacterial communities.

People who have more skin-dwelling bacteria have been shown to be more attractive to African

malaria mosquitoes, for example.

And one of those sweat compounds in particularlactic acidmight play a bigger role

in mosquito attraction than the others.

In a 2001 study in the journal Chemical Senses, researchers took sweat samples from 4 volunteers

and ranked them from most loved by mosquitoes to least loved.

The popular people were always popular: mosquitoes consistently buzzed to their samples, even

though they were collected on 28 different days over the course of a year.

And that seemed to be because of lactic acidthe most attractive sweat had between

three and five times more of it than the least attractive.

To test this idea, the researchers added lactic acid to samples that werent that attractive,

and low and behold, the mosquitoes suddenly thought those sweats are great.

More than 3 times as many mosquitoes chose an altered sweat sample over their previous favorite.

And that might have something to do with a special lactic acid sensor in a mosquitos

antenna called Ionotropic Receptor 8a, or just Ir8a for short.

When scientists genetically engineered mosquitoes to have a messed up Ir8a receptor, most didnt

fly towards samples of sweat containing lactic acid in a wind tunnel or towards sweaty human subjects.

And while theres some evidence that exercise raises lactic acid levels in a persons

sweat, in the end, it really comes down to how smelly you areand that comes down

to a complex mix of your genetics, microbiome, and hygiene behaviors.

Mosquito bites arent just annoying.

Every bite has the potential to pass along mosquito-carried infections toonasty

stuff like encephalitis, West Nile virus, yellow fever, and, of course, malaria.

But whats even more disturbing is that these pathogens seem to change something about

people to make them more attractive to the mosquitoes that spread them around.

For example, a 2005 study in PloS ONE found that more mosquitoes were attracted to kids

carrying the transmittable stage of malaria than to kids who had been naturally infected

with a non-infective stage or those who werent infected at all.

These differences disappeared when they treated all the kids with an antimalarial, so the

childrens individual mosquito attractiveness wasnt at play.

Although pretty scary, this finding isnt that surprising.

There are lots of examples in the animal world of parasites manipulating their host to help

them spread.

The big question is what the pathogen is changing to make the person its infecting more attractive.

Scientists think it ultimately comes down to odor, and a 2014 study using mice backed

up that hypothesis.

Researchers collected odor samples from both infected and non-infected mice over the course

of a malaria infection.

During the later stages of infection, when the parasite is transmittable, the mice produced

more smelly chemicals than in the early, non-transmittable stagesand were more attractive to the


And when researchers created different mixes of those chemicals and applied them to healthy

mice, those mice also became mosquito magnets.

The scientists were eventually able to figure out which chemicals were drawing the mosquitoes

in3-methyl butanoic acid, 2-methyl butanoic acid, hexanoic acid, and tridecane, in case

you were wondering.

But, of course, this was in mice.

So all the usual caveats about animal research apply.

Still, it shows there are infection-related changes that lure mosquitoes in.

And that means studies involving humans might be able to figure out exactly how these infections

make us more prone to bites.

Most of the things that make you a mosquito magnet arent all that easy to change.

But one thing is: your clothes.

A bunch of studies dating all the way back to the 1900s have shown that mosquitoes love

to land on dark colored surfaceseverything from painted barn roofs to boxes and, of course,


One of the earliest studies from 1947 had a guy stand in a mosquito infested room wearing

either a black, white, green, red, yellow, blue or tan shirt, while the researcher counted

how many mosquitoes landed on him.

Black, blue and red were the most attractive to mosquitoesthey didnt care as much

for yellow or white.

A later study from the early 1980s using differently-colored funnel traps found the same thing.

It also found that how much light reflected off the cloth determined how attractive the

traps werebasically, mosquitoes like things that arent super reflective.

Also, the mosquitoes seemed to like shorter wavelengths of light, in the 400 to 600 nanometer

rangebasically, violet to orange colorswhile anything with a wavelength over

600 nanometers was pretty much a no go.

So, you could opt for a light colored outfit or anything reflectivemaybe its time

to just bust out that sequined dress that turns you into a living disco ball.

For clarity, scientists havent explicitly tested whether sequins or shimmery fabrics

keep them at bay, but theres every reason to think they should.

And its thought that visual cues like color help mosquitoes spot a target from a greater

distance, particularly during the day.

One of the myths going around is that dark fabrics absorb more heat and so its the

temperature, not the color itself, that they love.

But a 2019 study found mosquitoes go for dark objects regardless of how warm they were.

That study needs to still be vetted by the scientific community but if it holds up, it

might help scientists figure out how much of a role these different cues play.

Another reason black is so popular is probably fairly simple: dark-colored objects generally

stand out more against their backgroundto a mosquito, anyway.

So, if shimmer isnt your thing, you could go the other way and wear something that will

help you blend in with your surroundingsmaybe go cammo!

Ive got some bad news for those summer

barbecues: turns out that if youre drinking booze, youre probably making yourself more

of a mosquito target.

This idea has been around for a long time, but it wasnt really tested in a controlled

manner until the early 2000s.

A 2002 study, published by the American Mosquito Control Association, found that more mosquitoes

landed on subjects after drinking a glass of beer than before.

The people were drinking beers, not the mosquitos

But, the researchers couldnt pinpoint why.

Their first thought was changes to skin temperature, since mosquitoes sense and are attracted to


Or, that the animals literally like the smell of alcohol.

The trouble is, they didnt find any links between how many mosquitoes landed on the

people and how warm they were or how much ethanol they had in their sweat.

A study in 2010 backed up the beer-increases-attractiveness finding.

And again temperature didnt seem to be a mediating factorin fact, on average,

people were colder after drinking.

That led the researchers back to this idea of smell.

But it wasnt the smell of ethanol itself, they argued.

Rather, they suggested that as alcohol metabolizes, it increases other chemicals in a persons

breath or sweat that make them a tastier-smelling target.

Though its not clear what these other chemicals are.

They also hypothesized that mosquitoes could have evolved to seek out these particular

aromas because they indicate lower physical defensesbasically, booze makes you less

coordinated, so you are bad at slapping the mosquito.

That sounds pretty logical, but a different study found no link between how defensive

a person isthat is, how much they tried to swat away a mosquitoand how many times

it tried to land on them.

Which isnt conclusive evidence against the idea, but it certainly doesnt support


Another potential explanation is that a boozed-up bloodstream makes for a more nutritious meal

somehow, so mosquitoes have evolved a way to detect thatthough, no study to date

has tested this directly.

Whatever the reason, it might be wise to skip the brewskis if youre hanging around outdoors.

Or, at least, cover up if you insist on a beer while barbecuing.

Just head to toe, wear one of those beekeeper outfits.

In the end, you cannot completely take yourself off a mosquitos radarwithout bug repellent,


But you can make yourself a little less temptinglike, by wearing the right clothes, or

being the Designated Driver.

And theres something else you might be able to do to lessen your chance of getting

bit: offer the mosquitoes around you a different snack.

Research published in 2019 in PLoS Biology found that feeding tiger mosquitoes sugar

lessened their attraction to people.

See, the whole reason female mosquitoes bite is that a blood meal gives them the extra

protein and nutrients they need to develop their eggs.

And in this case the sugar seemed to be meeting that nutritional need, though its not a

100% clear whether the sugar helped the females eggs develop or not.

Most intriguingly: sugar triggered a response in the mosquitoesgenes thats similar

to what happens after they feast on blood.

So maybe putting out some hummingbird feeders or dishes of cotton balls soaked with sugar-water

will make the mosquitoes near you less interested in your blood.

Though, yes, it might be attracting mosquitos around you and also youd be fueling those

mosquito baby-mommys.

So I guess its not a perfect solution.

Still, scientists are excited by this research because it means they might be able to identify

new genes involved in the mosquitoeshuman-seeking behavior, which could reveal new ways to control

their biting.

Because, in the end, while no one likes being bitten by mosquitoes, some itchy bumps are

the least of our worries.

Those mosquito-carried diseases kill around a million people every year.

So finding new and better ways to prevent mosquito bitesespecially for those who

are magnetscould save millions of people.

Making those summer outdoor activities all that more enjoyable is just a bonus.

Speaking of fun summer activities, if you need something to do on your next road trip,

you could try and stump your car with one of Brilliants Daily Challenges.

It will probably kill way more time than a game of I Spy, and youll get to learn something

about science, engineering, or math.

One of the latest challenges, for example, was about what kind of tire tracks different

unicycles leave.

It was a tough one!

Brilliant puts out new Challenges every day, and you can get the latest ones for free.

If you sign up for a Premium membership, youll also get access to the entire archivewhich

should be more than enough to get you to your destination.

If youre one of the first 200 people to sign up at, youll

get 20% off that annual Premium subscription, and youll be supporting SciShow along the way. So, thank you!

[ ♪OUTRO ]

The Description of 5 Things That Make You a Mosquito Magnet