1 00:00:02,040 --> 00:00:07,440 Speaker 1: Welcome to brain Stuff from how stuff works. Hey, brain stuff, 2 00:00:07,440 --> 00:00:11,280 Speaker 1: it's Christian Seger. If you're like most people, you hate mosquitoes. 3 00:00:11,520 --> 00:00:14,200 Speaker 1: They're kind of the Andy Dick of the insect world, 4 00:00:14,280 --> 00:00:19,079 Speaker 1: annoying and in some cases dangerous. If we rate animals 5 00:00:19,120 --> 00:00:22,680 Speaker 1: by the number of deaths they cause, these little blood 6 00:00:22,680 --> 00:00:25,880 Speaker 1: suckers top the charts by a wide margin, and this 7 00:00:25,960 --> 00:00:29,840 Speaker 1: is due to their transmission of malaria and other harmful diseases. 8 00:00:30,120 --> 00:00:33,600 Speaker 1: And whether your next mosquito bite causes serious illness or 9 00:00:33,680 --> 00:00:37,800 Speaker 1: intense frustration, we can all agree mosquitoes are just the worst. 10 00:00:38,159 --> 00:00:42,360 Speaker 1: But are some people immune to mosquito bites? First, let's 11 00:00:42,400 --> 00:00:46,839 Speaker 1: be clear mosquito bites aren't actually bites. When a mosquito 12 00:00:47,000 --> 00:00:50,280 Speaker 1: lands on you, she uses her probosis. It's a long, 13 00:00:50,520 --> 00:00:54,600 Speaker 1: double tubed mouthpiece to pierce your skin and get at 14 00:00:54,600 --> 00:00:58,480 Speaker 1: the blood underneath. And yes, that's a sheet. Every single 15 00:00:58,560 --> 00:01:02,120 Speaker 1: mosquito that has ever bit you has been female. They 16 00:01:02,200 --> 00:01:05,120 Speaker 1: bite you because they need a protein in your blood 17 00:01:05,200 --> 00:01:08,759 Speaker 1: to develop their eggs. When a mosquito uses her antenna 18 00:01:09,120 --> 00:01:12,000 Speaker 1: to sense the warm blood beneath your skin and then 19 00:01:12,080 --> 00:01:15,840 Speaker 1: pops her probosis in to tap your capillaries. One of 20 00:01:15,880 --> 00:01:20,400 Speaker 1: those tubes injects saliva, while the other one withdraws blood. 21 00:01:20,840 --> 00:01:25,040 Speaker 1: The saliva contains enzymes that act as a mild painkiller 22 00:01:25,319 --> 00:01:29,040 Speaker 1: and thins the blood to prevent clotting. Your body interprets 23 00:01:29,080 --> 00:01:34,640 Speaker 1: these enzymes as foreign invaders and produces histamine. Histamine binds 24 00:01:34,640 --> 00:01:39,000 Speaker 1: to receptors in the bite area, dilating local blood vessels. 25 00:01:39,360 --> 00:01:42,840 Speaker 1: This increased blood flow summons more white blood cells, and 26 00:01:42,880 --> 00:01:46,199 Speaker 1: when you get too much histamine, the bite area can 27 00:01:46,280 --> 00:01:51,320 Speaker 1: swell and redden, creating what's called a wheel. Yeah, wheel, 28 00:01:51,640 --> 00:01:54,880 Speaker 1: that's the word of the day. Now, each person will 29 00:01:54,920 --> 00:01:58,600 Speaker 1: react to a bite differently, and your allergies will vary. 30 00:01:58,760 --> 00:02:02,320 Speaker 1: So what makes a mosque to choose a certain person, Well, 31 00:02:02,760 --> 00:02:05,520 Speaker 1: there are a number of factors, one of the biggest 32 00:02:05,600 --> 00:02:09,560 Speaker 1: being that there are more than three thousand known varieties 33 00:02:09,600 --> 00:02:13,720 Speaker 1: of mosquitoes and they're not all looking for the same thing. 34 00:02:14,240 --> 00:02:18,040 Speaker 1: For those that dig a nice sip of human blood, smell, 35 00:02:18,440 --> 00:02:23,200 Speaker 1: body temperature, and genetics play huge roles. According to scientists 36 00:02:23,240 --> 00:02:27,600 Speaker 1: at Rotterdam Research, each human body can produce anywhere from 37 00:02:27,680 --> 00:02:32,560 Speaker 1: three hundred to four hundred distinct chemical odors, some of 38 00:02:32,560 --> 00:02:36,400 Speaker 1: which are bug magnets and others they might be bug repellent. 39 00:02:36,960 --> 00:02:41,279 Speaker 1: Research from a chemist named Ulrich Berner shows that mosquitoes 40 00:02:41,320 --> 00:02:46,600 Speaker 1: are particularly fond of carbon dioxide that's released from exhalation 41 00:02:46,720 --> 00:02:49,920 Speaker 1: and the skin, and they also like lactic acid, which 42 00:02:49,960 --> 00:02:54,640 Speaker 1: is present on our skin after exercise. Now, drinking beer, 43 00:02:54,840 --> 00:02:58,640 Speaker 1: being pregnant, and being a bigger person can all also 44 00:02:58,800 --> 00:03:03,239 Speaker 1: make you more active to mosquitoes. Diet and blood type 45 00:03:03,280 --> 00:03:07,239 Speaker 1: surprisingly don't seem to matter so much. Everybody has these 46 00:03:07,320 --> 00:03:10,360 Speaker 1: yummy chemicals on their body, but it seems that the 47 00:03:10,400 --> 00:03:16,040 Speaker 1: people mosquitoes avoid produced higher amounts of repellent chemicals. Dr 48 00:03:16,200 --> 00:03:19,840 Speaker 1: James Logan from Rotterdam set up a pretty weird experiment 49 00:03:19,880 --> 00:03:24,160 Speaker 1: to see if he could find these all important repellent chemicals. 50 00:03:24,200 --> 00:03:28,280 Speaker 1: His team separated people into two groups, mosquito favorites and 51 00:03:28,360 --> 00:03:33,240 Speaker 1: mosquito mez. They put these folks in body size foil 52 00:03:33,400 --> 00:03:36,960 Speaker 1: bags to collect their odors for two hours, and they 53 00:03:37,040 --> 00:03:40,840 Speaker 1: used a chromatograph to analyze the chemicals they had collected 54 00:03:41,120 --> 00:03:44,760 Speaker 1: and hooked electrodes up to mosquito antenna to see what 55 00:03:44,880 --> 00:03:48,200 Speaker 1: the bugs thought of each smell. They found about seven 56 00:03:48,280 --> 00:03:52,280 Speaker 1: or eight made a difference. These odors were present insignificantly 57 00:03:52,320 --> 00:03:56,720 Speaker 1: different quantities between those people who were attractive to mosquitoes 58 00:03:56,760 --> 00:03:59,880 Speaker 1: and those who weren't. Their study, published in the Journal 59 00:04:00,000 --> 00:04:05,920 Speaker 1: of Medical Entomology, cited two chemicals as significantly repellent, one 60 00:04:06,040 --> 00:04:11,160 Speaker 1: called six methyl five hepton to one, which apparently smells 61 00:04:11,240 --> 00:04:16,000 Speaker 1: of nail polish remover, and another called jennal acetone, which 62 00:04:16,080 --> 00:04:19,479 Speaker 1: has a kind of floral odor. As of this recording, 63 00:04:19,600 --> 00:04:22,400 Speaker 1: the race to use these and other chemicals as a 64 00:04:22,480 --> 00:04:26,479 Speaker 1: new superbug repellent is in full swing. So you probably 65 00:04:26,520 --> 00:04:30,279 Speaker 1: know that bacteria is largely responsible for the various smells 66 00:04:30,320 --> 00:04:33,640 Speaker 1: of the human body. Each human being is home to 67 00:04:33,760 --> 00:04:37,400 Speaker 1: a unique mix of trillions of microbes. It's sort of 68 00:04:37,440 --> 00:04:40,800 Speaker 1: like a fingerprint. Now, our genes may play a large 69 00:04:40,880 --> 00:04:44,120 Speaker 1: role in determining what sort of microbial life forms we 70 00:04:44,200 --> 00:04:48,360 Speaker 1: end up posting in. A team led by doctor Manuela 71 00:04:48,440 --> 00:04:55,159 Speaker 1: Fernandez Grandin tested the heritability of attractiveness to mosquitoes using twins. 72 00:04:55,640 --> 00:04:58,359 Speaker 1: The twins would put a hand into either end of 73 00:04:58,400 --> 00:05:03,080 Speaker 1: a sealed dome along with twenty female mosquitoes. Now don't worry, 74 00:05:03,120 --> 00:05:07,240 Speaker 1: they weren't allowed to bite. Researchers gave each subject an 75 00:05:07,240 --> 00:05:11,920 Speaker 1: attractiveness score compared to the other hand, identical twins had 76 00:05:11,960 --> 00:05:17,440 Speaker 1: consistently more similar scores compared to fraternal twins, so jeans 77 00:05:17,680 --> 00:05:20,520 Speaker 1: do seem to play a role. This may be tough 78 00:05:20,600 --> 00:05:24,160 Speaker 1: news for the or so of people that mosquitoes find 79 00:05:24,240 --> 00:05:28,920 Speaker 1: particularly attractive. If you're one of the local mosquito's favorite dishes, 80 00:05:29,240 --> 00:05:32,040 Speaker 1: remember to keep some kind of bug repellent with you 81 00:05:32,200 --> 00:05:35,360 Speaker 1: and to wear long sleeves and pants if the weather allows, 82 00:05:35,880 --> 00:05:38,880 Speaker 1: especially in areas of the world where these bugs carried 83 00:05:38,880 --> 00:05:43,000 Speaker 1: diseases like malaria or denge. And I suppose there's a 84 00:05:43,000 --> 00:05:46,480 Speaker 1: little light at the end of this mosquito net tunnel here. 85 00:05:46,920 --> 00:05:49,640 Speaker 1: Some people do have a chance of building up a 86 00:05:49,680 --> 00:05:54,520 Speaker 1: tolerance after repeated mosquito bites, but for others, the allergy 87 00:05:54,800 --> 00:06:03,440 Speaker 1: just gets worse. Check out the brainstuff channel on YouTube, 88 00:06:03,520 --> 00:06:05,679 Speaker 1: and for more on this and thousands of other topics, 89 00:06:05,880 --> 00:06:20,960 Speaker 1: visit howstuff works dot com.