What is in an Itch that makes it so appealing to scratch?

[Phlosphr]

I’m looking for a biological mechanism if at all possible. But I was wondering, I had a bout with dermatitis a while back and it itched like the dickens! I noticed that everytime I itched it I got a [for lack of better terminology] pleasurable feeling from scratching it. What’s up with that? Then I noticed it happened with mosquito bites and other itchy things?

Does anyone know the biological mechanisms for this? Am I releasing some sort of histamine or dopamine to the pleasure centers of my brain? What gives?

[panache45]

Ever since I started getting a buzz-cut, I’ve noticed that it’s really pleasurable to feel the clippers move over my head. And I’ve *always *found it very pleasurable when the barber shaves around the back and around my ears and sideburns. It’s almost like a mild sexual turn-on. And no, I don’t get any pleasure from shaving my face. And no, it doesn’t matter whether I’m attracted to the barber (actually my current barber is very hot, but that’s for another thread).

I know there are people who really do get sexually turned on by shaving or being shaved, but this is much more limited than that.

So what’s going on here?

[Queen_Tonya]

I always thought that the act of scratching is like a very small physical injury, prompting the release of pain-killing endorphins which relieves the itch sensation.

[CairoCarol]

A very similar question (“How do itches come about, and why does it feel good to scratch them?”) is asked in the “Ask The Experts” column of the June 2007 Scientific American. Unfortunately, the answer doesn’t address the pleasurable sensation, only “how scratching stops the itching.”

Itching generally involves activation of the pruriceptors of specialized nerve cells called C-fibers. These C-fibers are identical to those associated with the sensation of pain, but they are functionally distinct and only convey the itch sensation. When stimulated on the skin, the C-fibers carry signals along the nerve to the spinal cord and on to the brain.

Scratching and rubbing interfere with the sensations arising from pruriceptors by stimulating various pain and touch receptors in the same areas. Like many sensory systems in the body, activation of one signal, in this case that of the pain and touch receptors, causes “sourround inhibition” of another signal, that coming from the pruriceptor. This lack of pruriceptor firing “turns off” the itch sensation for a short period.

Okay, so we know why scratching stops an itch. But all we know about why it feels good is that it is (presumably) because the signal from touch receptors is being activated. Which rather uselessly tells us “being touched feels good.” Uh-huh. And the reason is…?

I love SciAm, but I can’t imagine Cecil leaving a question half-answered like that.

[Qazzz]

@panache45

Ever since I started getting a buzz-cut, I’ve noticed that it’s really pleasurable to feel the clippers move over my head. And I’ve *always *found it very pleasurable when the barber shaves around the back and around my ears and sideburns. It’s almost like a mild sexual turn-on. And no, I don’t get any pleasure from shaving my face. And no, it doesn’t matter whether I’m attracted to the barber (actually my current barber is very hot, but that’s for another thread).

I know there are people who really do get sexually turned on by shaving or being shaved, but this is much more limited than that.

So what’s going on here?

I totally agree. It’s almost worth the price of an entire haircut just to have the razor dragging across the back of my neck. Sends chills of pleasure down my spine.