Some itches, of course, are perfectly pleasant, particularly those that can be easily scratched.
But all itches, low-level or consuming, present the same question: why?
Why do we itch?
Illustration: Benjamin Currie/Gizmodo
What is its evolutionary purpose?
For this weeksGiz Asks, we reached out to a number of experts to find out.
This article was originally published on May 3, 2021.
Then theres the question of why scratching an itch often feels quite good.
In the brain, these chemical signals are interpreted as itch.
Occasionally, your itch nerves can be damaged or diseased and will simply trigger unsolicited itch sensations.
In this case, people feel itchy even without a rash.
Itch is similar to pain in the sense that both are considered noxious, or unpleasant, stimuli.
However, our behavioral response to each is different.
To pain, we respond with withdrawal.
To itch, our response is to scratch.
Thats the definition of itch: any sensation that causes a desire to scratch.
So what causes itch?
More practically, dermatologists broadly think of itch in two categories: itch with rash and itch without rash.
In these cases, it can be an issue of the sensory nerves or the central nervous system itself.
Itch that is purely related to nerve problems is not uncommon.
There is a phenomenon termed pruritus of the elderly.
(Pruritus is the clinical term for itch.)
Another example is spinal cord abnormalities leading to the sensation of itch.
We dont really understand it, but its really interesting.
Do you have a burning question for Giz Asks?
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