What is the underlying physiological mechanism of itch?

[mktsgm]

TL;DR Summary

Is there a purpose or objective behind bodily itching? How does a scratch differ from urticaria from the pathophysiological point of view?

What is the dermatological condition called severe itch or urticaria? What is its underlying pathophysiological mechanism?

While a simple scratch may be a compulsory reflex, it may reward a pleasurable experience. How it is different from an itch, which is considered a pathological condition.

Is it a condition (itching) by itself or is it a reflexive behavior of the body in response to something else? Is it a part of the immunological response as histamines are heavily involved? If so, what the body is trying to remove?

Is there an evolutionary purpose and objective behind them?

thanks in advance,

 

[.Scott]

Over the past couple of decades, I have managed to stay away from poison ivy . But before that and especially as a teenager, I caught it quite regularly. There is a pretty strong impulse to scratch the poison ivy - in direct contradiction to all common advice.

So here's the problem: This forum cannot be used to dispense medical advise. You aren't asking for medical advise - but it's really hard to answer your first question (purpose of itch) without it sounding like advice. Worse yet, if you do take the answer as advice, it would in all likelihood be the absolutely wrong advise.

That said:

The most direct and immediate result of scratching the poison ivy is to break the skins surface (the blisters) and spread the underlying fluid. That underlying fluid is the immune system attack force. Certainly the simplest explanation for the itch is to provide you with a conscious signal for your deliberate assistance in getting that fluid to the surface. I'm not saying that's a good idea, but it is the most apparent purpose of the itch. And if you don't scratch, in all but the mildest cases, some of the fluid will make it to the surface anyway.

 

[BillTre]

I would guess the evolutionary origin of scratching lies in something like a scratch reflex to get rid of ecto-parasites (like bugs or ticks biting you). This is a basic kind of behavior, directed toward protecting the body.
Such behaviors are usually triggered by some surface mechanical stimulus to the body. In flies, moving a single sensory hair can elicit grooming behavior for that area.

In people, there are probably a lot of stimuli (insect bite, localized inflammation, etc.) from the body surface that can trigger itching behaviors.

If the response (itching) is not terminated in a timely manner, it may continue for inappropriately long periods of time and cause problems.

 

[pinball1970]

Summary: Is there a purpose or objective behind bodily itching? How does a scratch differ from urticaria from the pathophysiological point of view?

What is the dermatological condition called severe itch or urticaria? What is its underlying pathophysiological mechanism?

While a simple scratch may be a compulsory reflex, it may reward a pleasurable experience. How it is different from an itch, which is considered a pathological condition.

Is it a condition (itching) by itself or is it a reflexive behavior of the body in response to something else? Is it a part of the immunological response as histamines are heavily involved? If so, what the body is trying to remove?

Is there an evolutionary purpose and objective behind them?

thanks in advance,

For the evolutionary part, just a thought.
Chemical injury aside, ( insect bite, nettles etc) contact with the skin with a feather say may itch you but not be unpleasant or injurious.

The nervous system will tell the brain” contact” and your developmental skill and experience can decide whether there is a an issue.

That blade of grass could also be ant.

 

[pinball1970]

Summary: Is there a purpose or objective behind bodily itching? How does a scratch differ from urticaria from the pathophysiological point of view?

What is the dermatological condition called severe itch or urticaria? What is its underlying pathophysiological mechanism?

While a simple scratch may be a compulsory reflex, it may reward a pleasurable experience. How it is different from an itch, which is considered a pathological condition.

Is it a condition (itching) by itself or is it a reflexive behavior of the body in response to something else? Is it a part of the immunological response as histamines are heavily involved? If so, what the body is trying to remove?

Is there an evolutionary purpose and objective behind them?

thanks in advance,

I remembered something last night and checked it out this morning

https://www.nobelprize.org/uploads/2021/10/advanced-medicine-2021.pdf

Itching specifically

https://www.ncbi.nlm.nih.gov/pmc/ar...hysiology is encompassed,cycle is removed (1).