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Uploaded:2014-03-04
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Hank explores a vexing question asked at picnics and beach parties everywhere: Why do bug bites itch? To help you understand the answer, he takes you into the blow by blow of a bug bite which, we warn you, is pretty horrifying.
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Sources:
http://www.cdc.gov/niosh/topics/insects/
http://phenomena.nationalgeographic.com/2013/08/06/heres-what-happens-inside-you-when-a-mosquito-bites/
http://www.astrographics.com/GalleryPrintsIndex/GP2108.html
http://www.news-medical.net/health/What-is-Histamine.aspx
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2519061/
Here's a vexing question asked at picnics and beach parties everywhere: "Why do bug bites itch?"   And the answer is:  They don't.   Bug bites don't itch at all, sometimes you don't even feel them, and that's pretty amazing because what goes on under your skin when a bug bites you is horrifying. Alright, some insects, like certain kinds of ants, are venomous so their bites can itch because their venom contains formic acid, which can irritate and blister the skin.   But let's talk about Nematocera, the suborder of insects that includes black flies and mosquitoes. These bugs have a long bendable proboscis that they stick into you to drink your blood. The proboscis is made up of six different mouth parts.  First you got the mandibles which are hooked and the two maxillae which are serrated like steak knives. These sharp bits go as deep as they can to make an opening for the other two mouth parts to pass through -- the labrum and the hypopharynx. Those are both long, hollow, flexible tubes and they wriggle around inside of you like a worm while the bug probes around for blood vessels.   Once it finds one, blood gets sucked up through the labrum, and saliva is ejected down through the hypopharynx.  That saliva is an anti-coagulant; it stops your blood from clotting inside the bug's proboscis so that it can keep drinking. It is also the main vector for diseases that are transmitted by mosquitoes like Malaria and West Nile Virus. And it has one other awesome property: you are probably allergic to it, and when you're allergic to something your body produces histamine, the protein that triggers inflammation and widens your capillaries to allow white blood cells to pass through them so that they can fight foreign invaders.   So, it's the histamine that makes you swell up and itch when you get a bug bite, just like it makes your eyes and nose itch during pollen season. We're not even sure why histamine needs to make you itchy in order to do its job.  It might just be your body's way of telling you that something's wrong with your skin. But I'm pretty sure we all wish it would stop.   So thanks for asking, and thanks to all of our Subbable subscribers who make this and everything you see here on SciShow possible.  If you have a quick question that you'd like us to answer, let us know. You can find us on Facebook and Twitter and as always in the comments below. And if you want to keep getting smarter with us here at SciShow, you can go to youtube.com/scishow and subscribe.