1 00:00:02,040 --> 00:00:09,720 Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey everybody, 2 00:00:09,760 --> 00:00:12,719 Speaker 1: I'm Christian Seger and this is the brain stuff where 3 00:00:12,760 --> 00:00:15,880 Speaker 1: I tell you about itching. Why do we itch? Why 4 00:00:16,000 --> 00:00:19,439 Speaker 1: does it feel so good to scratch an itch? Well, 5 00:00:19,640 --> 00:00:22,159 Speaker 1: to answer this, we must first turn to one of 6 00:00:22,200 --> 00:00:28,040 Speaker 1: the body's most unappreciated, hardworking organs, the skin. So let's 7 00:00:28,080 --> 00:00:31,639 Speaker 1: start with your skin, the original clothing, your birthday suit. 8 00:00:32,040 --> 00:00:36,240 Speaker 1: Skin is pretty cool stuff. It is your body's largest organ. 9 00:00:36,600 --> 00:00:38,519 Speaker 1: If you were to stretch out the skin of the 10 00:00:38,600 --> 00:00:41,159 Speaker 1: average adult, you know, like if you wanted to make 11 00:00:41,200 --> 00:00:44,159 Speaker 1: some cool book bindings or masks or sheets or whatever, 12 00:00:44,560 --> 00:00:48,279 Speaker 1: you stretch that out, that would cover twenty two square 13 00:00:48,360 --> 00:00:52,280 Speaker 1: feet and weigh eight pounds. That's about enough to cover 14 00:00:52,320 --> 00:00:55,600 Speaker 1: the twin bed in a creepy Serial Killers apartment. But 15 00:00:55,680 --> 00:00:58,320 Speaker 1: while it's still attached to your body, skin protects you 16 00:00:58,400 --> 00:01:03,360 Speaker 1: from germs signals. The immune system regulates body temperature and 17 00:01:03,520 --> 00:01:07,520 Speaker 1: allows us to experience the crucial sense known as touch. 18 00:01:08,120 --> 00:01:11,560 Speaker 1: One type of nerve ending in particular, is responsible for 19 00:01:11,600 --> 00:01:14,960 Speaker 1: the sensation of itching. Now, as it turns out, and 20 00:01:15,160 --> 00:01:20,120 Speaker 1: itch is just the street name for something called paritis. Yeah, 21 00:01:20,120 --> 00:01:23,400 Speaker 1: it's difficult to say. It is the irritation of skin 22 00:01:23,560 --> 00:01:28,880 Speaker 1: cells or associated nerve cells caused by some external stimuli, 23 00:01:29,360 --> 00:01:33,119 Speaker 1: like say tickling. Itching is a built in defense mechanism 24 00:01:33,160 --> 00:01:36,480 Speaker 1: that alerts your body to the potential of being harmed. 25 00:01:36,920 --> 00:01:39,800 Speaker 1: Think of that feeling you get when an insect crawls 26 00:01:39,920 --> 00:01:43,560 Speaker 1: along your skin. That's your body saying watch out, that 27 00:01:43,600 --> 00:01:46,600 Speaker 1: bug is out for your blood. Now, this itching sensation 28 00:01:46,760 --> 00:01:51,280 Speaker 1: comes from per receptors. Yeah, remember the whole peritis thing. 29 00:01:51,520 --> 00:01:54,720 Speaker 1: That's just as difficult to say, But these are specialized 30 00:01:54,800 --> 00:01:58,600 Speaker 1: nerve endings in your skin. Let's stick with this insect example. 31 00:01:58,840 --> 00:02:01,560 Speaker 1: When the bug lands your skin, it may not bother 32 00:02:01,680 --> 00:02:04,360 Speaker 1: you at first, but soon it will begin to rub 33 00:02:04,400 --> 00:02:07,280 Speaker 1: back and forth across your skin as it walks along 34 00:02:07,360 --> 00:02:10,440 Speaker 1: looking for the best place to bite you. Once the 35 00:02:10,480 --> 00:02:14,720 Speaker 1: bug scratches your skin, surface layer receptors in the dermis 36 00:02:14,800 --> 00:02:18,519 Speaker 1: of the skin will become irritated. In a split second, 37 00:02:18,600 --> 00:02:21,880 Speaker 1: these receptors send a signal through fibers in the skin 38 00:02:21,960 --> 00:02:24,919 Speaker 1: to your spinal cord and then up to the cerebral 39 00:02:24,960 --> 00:02:28,400 Speaker 1: cortex in your brain. The same fibers that send itching 40 00:02:28,440 --> 00:02:31,640 Speaker 1: signals are also used to send pain signals to the brain, 41 00:02:31,720 --> 00:02:35,040 Speaker 1: which once led some scientists to believe that itching was 42 00:02:35,080 --> 00:02:38,639 Speaker 1: a form of light pain. That notion has since been 43 00:02:38,639 --> 00:02:42,560 Speaker 1: dispelled by research which showed that pain and itching illicit 44 00:02:42,680 --> 00:02:47,680 Speaker 1: opposite responses. Pain causes us to withdraw, an itching causes 45 00:02:47,800 --> 00:02:50,720 Speaker 1: us to scratch. As soon as we feel an itch, 46 00:02:50,880 --> 00:02:54,320 Speaker 1: our first natural response is to scratch the spot of 47 00:02:54,400 --> 00:02:57,920 Speaker 1: the itch with our fingernails. The reason for this response 48 00:02:58,040 --> 00:03:01,040 Speaker 1: is simple, We want to remove the irritant as soon 49 00:03:01,200 --> 00:03:05,360 Speaker 1: as possible. Once you've scratched the area of irritation, you 50 00:03:05,360 --> 00:03:09,000 Speaker 1: are likely to feel some relief When your brain realizes 51 00:03:09,080 --> 00:03:12,160 Speaker 1: that you've scratched away the irritant, the signal being sent 52 00:03:12,240 --> 00:03:15,040 Speaker 1: to your brain that you have an itch is interrupted 53 00:03:15,080 --> 00:03:19,720 Speaker 1: and therefore no longer recognized. Even if you don't remove 54 00:03:19,800 --> 00:03:23,560 Speaker 1: the irritant, scratching will at least cause pain and divert 55 00:03:23,639 --> 00:03:27,120 Speaker 1: your attention away from the itching. The irritant that caused 56 00:03:27,160 --> 00:03:30,640 Speaker 1: the itching is very small, maybe only a few microns 57 00:03:30,639 --> 00:03:34,000 Speaker 1: in length, so it only disturbs a few nerve endings. 58 00:03:34,280 --> 00:03:37,160 Speaker 1: When you use your fingernail to scratch the spot where 59 00:03:37,160 --> 00:03:40,200 Speaker 1: the irritant is, you not only remove the irritant, but 60 00:03:40,360 --> 00:03:44,560 Speaker 1: you irritate a lot more nerve endings than the irritant. 61 00:03:44,960 --> 00:03:48,360 Speaker 1: In many cases, an itching sensation can be related to 62 00:03:48,520 --> 00:03:52,920 Speaker 1: various ailments or diseases, from dry skin or poison ivy 63 00:03:52,960 --> 00:03:57,920 Speaker 1: to more serious, life threatening internal issues. So if you 64 00:03:57,960 --> 00:04:04,240 Speaker 1: have continual chron paritis, visit your local medical professional. They 65 00:04:04,280 --> 00:04:06,640 Speaker 1: should be able to help you find a solution, which 66 00:04:06,720 --> 00:04:09,360 Speaker 1: is great because we all know there are a few 67 00:04:09,400 --> 00:04:17,480 Speaker 1: things worse than an itch you can't scratch. Check out 68 00:04:17,520 --> 00:04:19,680 Speaker 1: the brainstuff channel on YouTube, and for more on this 69 00:04:19,839 --> 00:04:36,720 Speaker 1: and thousands of other topics, visit how stuff works dot com.