Speaker 1: Welcome to brain Stuff from how stuff works. Hey, brain stuff,
Speaker 1: it's Christian Seger. If you're like most people, you hate mosquitoes.
Speaker 1: They're kind of the Andy Dick of the insect world,
Speaker 1: annoying and in some cases dangerous. If we rate animals
Speaker 1: by the number of deaths they cause, these little blood
Speaker 1: suckers top the charts by a wide margin, and this
Speaker 1: is due to their transmission of malaria and other harmful diseases.
Speaker 1: And whether your next mosquito bite causes serious illness or
Speaker 1: intense frustration, we can all agree mosquitoes are just the worst.
Speaker 1: But are some people immune to mosquito bites? First, let's
Speaker 1: be clear mosquito bites aren't actually bites. When a mosquito
Speaker 1: lands on you, she uses her probosis. It's a long,
Speaker 1: double tubed mouthpiece to pierce your skin and get at
Speaker 1: the blood underneath. And yes, that's a sheet. Every single
Speaker 1: mosquito that has ever bit you has been female. They
Speaker 1: bite you because they need a protein in your blood
Speaker 1: to develop their eggs. When a mosquito uses her antenna
Speaker 1: to sense the warm blood beneath your skin and then
Speaker 1: pops her probosis in to tap your capillaries. One of
Speaker 1: those tubes injects saliva, while the other one withdraws blood.
Speaker 1: The saliva contains enzymes that act as a mild painkiller
Speaker 1: and thins the blood to prevent clotting. Your body interprets
Speaker 1: these enzymes as foreign invaders and produces histamine. Histamine binds
Speaker 1: to receptors in the bite area, dilating local blood vessels.
Speaker 1: This increased blood flow summons more white blood cells, and
Speaker 1: when you get too much histamine, the bite area can
Speaker 1: swell and redden, creating what's called a wheel. Yeah, wheel,
Speaker 1: that's the word of the day. Now, each person will
Speaker 1: react to a bite differently, and your allergies will vary.
Speaker 1: So what makes a mosque to choose a certain person, Well,
Speaker 1: there are a number of factors, one of the biggest
Speaker 1: being that there are more than three thousand known varieties
Speaker 1: of mosquitoes and they're not all looking for the same thing.
Speaker 1: For those that dig a nice sip of human blood, smell,
Speaker 1: body temperature, and genetics play huge roles. According to scientists
Speaker 1: at Rotterdam Research, each human body can produce anywhere from
Speaker 1: three hundred to four hundred distinct chemical odors, some of
Speaker 1: which are bug magnets and others they might be bug repellent.
Speaker 1: Research from a chemist named Ulrich Berner shows that mosquitoes
Speaker 1: are particularly fond of carbon dioxide that's released from exhalation
Speaker 1: and the skin, and they also like lactic acid, which
Speaker 1: is present on our skin after exercise. Now, drinking beer,
Speaker 1: being pregnant, and being a bigger person can all also
Speaker 1: make you more active to mosquitoes. Diet and blood type
Speaker 1: surprisingly don't seem to matter so much. Everybody has these
Speaker 1: yummy chemicals on their body, but it seems that the
Speaker 1: people mosquitoes avoid produced higher amounts of repellent chemicals. Dr
Speaker 1: James Logan from Rotterdam set up a pretty weird experiment
Speaker 1: to see if he could find these all important repellent chemicals.
Speaker 1: His team separated people into two groups, mosquito favorites and
Speaker 1: mosquito mez. They put these folks in body size foil
Speaker 1: bags to collect their odors for two hours, and they
Speaker 1: used a chromatograph to analyze the chemicals they had collected
Speaker 1: and hooked electrodes up to mosquito antenna to see what
Speaker 1: the bugs thought of each smell. They found about seven
Speaker 1: or eight made a difference. These odors were present insignificantly
Speaker 1: different quantities between those people who were attractive to mosquitoes
Speaker 1: and those who weren't. Their study, published in the Journal
Speaker 1: of Medical Entomology, cited two chemicals as significantly repellent, one
Speaker 1: called six methyl five hepton to one, which apparently smells
Speaker 1: of nail polish remover, and another called jennal acetone, which
Speaker 1: has a kind of floral odor. As of this recording,
Speaker 1: the race to use these and other chemicals as a
Speaker 1: new superbug repellent is in full swing. So you probably
Speaker 1: know that bacteria is largely responsible for the various smells
Speaker 1: of the human body. Each human being is home to
Speaker 1: a unique mix of trillions of microbes. It's sort of
Speaker 1: like a fingerprint. Now, our genes may play a large
Speaker 1: role in determining what sort of microbial life forms we
Speaker 1: end up posting in. A team led by doctor Manuela
Speaker 1: Fernandez Grandin tested the heritability of attractiveness to mosquitoes using twins.
Speaker 1: The twins would put a hand into either end of
Speaker 1: a sealed dome along with twenty female mosquitoes. Now don't worry,
Speaker 1: they weren't allowed to bite. Researchers gave each subject an
Speaker 1: attractiveness score compared to the other hand, identical twins had
Speaker 1: consistently more similar scores compared to fraternal twins, so jeans
Speaker 1: do seem to play a role. This may be tough
Speaker 1: news for the or so of people that mosquitoes find
Speaker 1: particularly attractive. If you're one of the local mosquito's favorite dishes,
Speaker 1: remember to keep some kind of bug repellent with you
Speaker 1: and to wear long sleeves and pants if the weather allows,
Speaker 1: especially in areas of the world where these bugs carried
Speaker 1: diseases like malaria or denge. And I suppose there's a
Speaker 1: little light at the end of this mosquito net tunnel here.
Speaker 1: Some people do have a chance of building up a
Speaker 1: tolerance after repeated mosquito bites, but for others, the allergy
Speaker 1: just gets worse. Check out the brainstuff channel on YouTube,
Speaker 1: and for more on this and thousands of other topics,
Speaker 1: visit howstuff works dot com.