Welcome to brain Stuff from How Stuff Works. Hey everybody, I'm Christian Seger and this is the brain stuff where I tell you about itching. Why do we itch? Why does it feel so good to scratch an itch? Well, to answer this, we must first turn to one of the body's most unappreciated, hardworking organs, the skin. So let's start with your skin, the original clothing, your birthday suit. Skin is pretty cool stuff. It is your body's largest organ.
If you were to stretch out the skin of the average adult, you know, like if you wanted to make some cool book bindings or masks or sheets or whatever, you stretch that out, that would cover twenty two square feet and weigh eight pounds. That's about enough to cover the twin bed in a creepy Serial Killers apartment. But while it's still attached to your body, skin protects you
from germs signals. The immune system regulates body temperature and allows us to experience the crucial sense known as touch. One type of nerve ending in particular, is responsible for the sensation of itching. Now, as it turns out, and itch is just the street name for something called paritis. Yeah, it's difficult to say. It is the irritation of skin cells or associated nerve cells caused by some external stimuli,
like say tickling. Itching is a built in defense mechanism that alerts your body to the potential of being harmed. Think of that feeling you get when an insect crawls along your skin. That's your body saying watch out, that bug is out for your blood. Now, this itching sensation comes from per receptors. Yeah, remember the whole peritis thing. That's just as difficult to say, But these are specialized nerve endings in your skin. Let's stick with this insect example.
When the bug lands your skin, it may not bother you at first, but soon it will begin to rub back and forth across your skin as it walks along looking for the best place to bite you. Once the bug scratches your skin, surface layer receptors in the dermis of the skin will become irritated. In a split second, these receptors send a signal through fibers in the skin to your spinal cord and then up to the cerebral
cortex in your brain. The same fibers that send itching signals are also used to send pain signals to the brain, which once led some scientists to believe that itching was a form of light pain. That notion has since been dispelled by research which showed that pain and itching illicit opposite responses. Pain causes us to withdraw, an itching causes us to scratch. As soon as we feel an itch, our first natural response is to scratch the spot of
the itch with our fingernails. The reason for this response is simple, We want to remove the irritant as soon as possible. Once you've scratched the area of irritation, you are likely to feel some relief When your brain realizes that you've scratched away the irritant, the signal being sent to your brain that you have an itch is interrupted and therefore no longer recognized. Even if you don't remove the irritant, scratching will at least cause pain and divert
your attention away from the itching. The irritant that caused the itching is very small, maybe only a few microns in length, so it only disturbs a few nerve endings. When you use your fingernail to scratch the spot where the irritant is, you not only remove the irritant, but you irritate a lot more nerve endings than the irritant. In many cases, an itching sensation can be related to various ailments or diseases, from dry skin or poison ivy
to more serious, life threatening internal issues. So if you have continual chron paritis, visit your local medical professional. They should be able to help you find a solution, which is great because we all know there are a few things worse than an itch you can't scratch. Check out the brainstuff channel on YouTube, and for more on this and thousands of other topics, visit how stuff works dot com.