BrainStuff Classics: Why Do We Itch?

The sensation of itchiness can be maddening. Learn what's going on in your nerves and brain when you itch -- and when you scratch that itch -- in this classic episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,
I'm Lauren vocal Bam, and I've got another brain Stuff
classic episode for you today from our former host, Christian Sager.
The topic why do we Itch? Hey everybody, I'm Christian

(00:22):
Sager 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.

(00:46):
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 air 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

(01:08):
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

(01:28):
name for something called paritis. Yet 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

(01:49):
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 receptors. Yeah,
remember the whole paritis 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 on

(02:11):
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

(02:35):
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

(02:56):
causes us to withdraw, and 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

(03:17):
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

(03:40):
very small, maybe only a few microns in length, so
it only disturbs a few nerve endings When you use
your finger nail 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,

(04:02):
from dry skin or poison ivy to more serious life
threatening internal issues. So if you have continual chronic 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

(04:22):
itch you can't scratch. Today's episode was written by Ben
Bolan and produced by Tyler Clang. Check out our online
shop at t public dot com slash Brainstuff. Every purchase
supports us directly, and of course, for more on this
and lots of other topics that will get unto your
skin in a good way, visit our home planet, how

(04:43):
stuff works dot com.