WEBVTT - Why Do We Itch?

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<v Speaker 1>Welcome to brain Stuff from How Stuff Works. Hey everybody,

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<v Speaker 1>I'm Christian Seger and this is the brain stuff where

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<v Speaker 1>I tell you about itching. Why do we itch? Why

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<v Speaker 1>does it feel so good to scratch an itch? Well,

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<v Speaker 1>to answer this, we must first turn to one of

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<v Speaker 1>the body's most unappreciated, hardworking organs, the skin. So let's

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<v Speaker 1>start with your skin, the original clothing, your birthday suit.

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<v Speaker 1>Skin is pretty cool stuff. It is your body's largest organ.

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<v Speaker 1>If you were to stretch out the skin of the

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<v Speaker 1>average adult, you know, like if you wanted to make

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<v Speaker 1>some cool book bindings or masks or sheets or whatever,

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<v Speaker 1>you stretch that out, that would cover twenty two square

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<v Speaker 1>feet and weigh eight pounds. That's about enough to cover

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<v Speaker 1>the twin bed in a creepy Serial Killers apartment. But

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<v Speaker 1>while it's still attached to your body, skin protects you

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<v Speaker 1>from germs signals. The immune system regulates body temperature and

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<v Speaker 1>allows us to experience the crucial sense known as touch.

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<v Speaker 1>One type of nerve ending in particular, is responsible for

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<v Speaker 1>the sensation of itching. Now, as it turns out, and

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<v Speaker 1>itch is just the street name for something called paritis. Yeah,

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<v Speaker 1>it's difficult to say. It is the irritation of skin

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<v Speaker 1>cells or associated nerve cells caused by some external stimuli,

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<v Speaker 1>like say tickling. Itching is a built in defense mechanism

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<v Speaker 1>that alerts your body to the potential of being harmed.

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<v Speaker 1>Think of that feeling you get when an insect crawls

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<v Speaker 1>along your skin. That's your body saying watch out, that

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<v Speaker 1>bug is out for your blood. Now, this itching sensation

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<v Speaker 1>comes from per receptors. Yeah, remember the whole peritis thing.

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<v Speaker 1>That's just as difficult to say, But these are specialized

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<v Speaker 1>nerve endings in your skin. Let's stick with this insect example.

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<v Speaker 1>When the bug lands your skin, it may not bother

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<v Speaker 1>you at first, but soon it will begin to rub

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<v Speaker 1>back and forth across your skin as it walks along

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<v Speaker 1>looking for the best place to bite you. Once the

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<v Speaker 1>bug scratches your skin, surface layer receptors in the dermis

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<v Speaker 1>of the skin will become irritated. In a split second,

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<v Speaker 1>these receptors send a signal through fibers in the skin

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<v Speaker 1>to your spinal cord and then up to the cerebral

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<v Speaker 1>cortex in your brain. The same fibers that send itching

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<v Speaker 1>signals are also used to send pain signals to the brain,

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<v Speaker 1>which once led some scientists to believe that itching was

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<v Speaker 1>a form of light pain. That notion has since been

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<v Speaker 1>dispelled by research which showed that pain and itching illicit

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<v Speaker 1>opposite responses. Pain causes us to withdraw, an itching causes

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<v Speaker 1>us to scratch. As soon as we feel an itch,

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<v Speaker 1>our first natural response is to scratch the spot of

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<v Speaker 1>the itch with our fingernails. The reason for this response

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<v Speaker 1>is simple, We want to remove the irritant as soon

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<v Speaker 1>as possible. Once you've scratched the area of irritation, you

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<v Speaker 1>are likely to feel some relief When your brain realizes

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<v Speaker 1>that you've scratched away the irritant, the signal being sent

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<v Speaker 1>to your brain that you have an itch is interrupted

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<v Speaker 1>and therefore no longer recognized. Even if you don't remove

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<v Speaker 1>the irritant, scratching will at least cause pain and divert

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<v Speaker 1>your attention away from the itching. The irritant that caused

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<v Speaker 1>the itching is very small, maybe only a few microns

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<v Speaker 1>in length, so it only disturbs a few nerve endings.

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<v Speaker 1>When you use your fingernail to scratch the spot where

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<v Speaker 1>the irritant is, you not only remove the irritant, but

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<v Speaker 1>you irritate a lot more nerve endings than the irritant.

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<v Speaker 1>In many cases, an itching sensation can be related to

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<v Speaker 1>various ailments or diseases, from dry skin or poison ivy

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<v Speaker 1>to more serious, life threatening internal issues. So if you

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<v Speaker 1>have continual chron paritis, visit your local medical professional. They

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<v Speaker 1>should be able to help you find a solution, which

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<v Speaker 1>is great because we all know there are a few

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<v Speaker 1>things worse than an itch you can't scratch. Check out

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<v Speaker 1>the brainstuff channel on YouTube, and for more on this

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<v Speaker 1>and thousands of other topics, visit how stuff works dot com.