What is the underlying physiological mechanism of itch?

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In summary: 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
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mktsgm
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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,
 
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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.
 
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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.
 
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mktsgm said:
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.
 
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mktsgm said:
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).
 
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1. What causes the sensation of itch?

The sensation of itch is caused by the activation of specialized nerve fibers called C-fibers. These fibers transmit signals from the skin to the spinal cord, which then relays the signal to the brain. Itch can also be triggered by certain chemicals, such as histamine, released by the immune system in response to an irritant.

2. How does the body respond to itch?

When the C-fibers are activated, they release a chemical called neuropeptide, which causes the surrounding skin to become inflamed and triggers the urge to scratch. Scratching the affected area provides temporary relief by disrupting the signals being sent to the brain.

3. What role do histamines play in itch?

Histamines are chemicals released by the immune system in response to an irritant or allergen. They bind to specific receptors in the skin and trigger the release of neuropeptide, which causes the sensation of itch. Antihistamines work by blocking these receptors and reducing the release of neuropeptide, providing relief from itch.

4. Can psychological factors contribute to itch?

Yes, psychological factors such as stress, anxiety, and depression can contribute to the sensation of itch. These emotions can activate the body's stress response, which can increase the release of neuropeptide and intensify the sensation of itch.

5. How is itch different from pain?

While itch and pain can both be unpleasant sensations, they are mediated by different nerve fibers and serve different purposes. Pain is a protective response to potential tissue damage, while itch is a response to an irritant or allergen. Additionally, pain is typically localized to a specific area, while itch can be felt over a larger area of the skin.

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