How does an ice pack reduce swelling and promote healing in injured areas?

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Discussion Overview

The discussion centers on the mechanisms by which ice packs reduce swelling and promote healing in injured areas. Participants explore various aspects of cold therapy, including its effects on blood flow, pain sensation, and cellular damage, as well as comparisons with other methods like dry ice and liquid nitrogen.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that ice packs numb the injured area, potentially reducing sensory signals to the central nervous system.
  • Others argue that ice packs constrict blood vessels, reducing blood flow and inhibiting swelling, which may also prevent further damage.
  • It is suggested that the cold can freeze water in cells, causing them to burst and die, which may relate to the sensation of burning associated with extreme cold.
  • Some participants discuss the use of cold caps during chemotherapy, noting that they constrict blood vessels to limit the effect of chemotherapeutic agents on hair follicles, although this may risk allowing metastases to escape treatment.
  • There is a question about whether the burning sensation from cold is similar to that from heat, with some suggesting that both are pain sensations linked to nerve stimulation.
  • One participant explains that ice packs reduce swelling by causing the contraction of dilated blood vessels, thereby limiting the inflammatory response and circulation of white blood cells.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the mechanisms of cold therapy, particularly concerning the relationship between cold application, pain sensation, and the physiological responses to injury. The discussion remains unresolved with no consensus on all points raised.

Contextual Notes

Some claims depend on specific definitions of pain and injury response, and there are unresolved questions about the exact mechanisms by which cold affects cellular processes and pain perception.

pivoxa15
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It is common to see children when hurt while playing given ice packs to the injured area. Why is this coldness good? Does it numb the injured area so sensory signals less frequently reach the central nervous system?

Also dry ice such as CO2 is able to 'burn' skin because of its very low temperture, not through any chemical effect. It has been used in the past by doctors to remove warts and even small skin cancers. How does dry ice 'burn' skin? How does it remove what they claim is it the burning effect?

The article said that these days liquid nitrogen is used instead of CO2 as it is far colder and temporarily anaesthetises the skin - which goes back to my first question? It also burn warts and cancers more effectively.
 
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pivoxa15 said:
It is common to see children when hurt while playing given ice packs to the injured area. Why is this coldness good? Does it numb the injured area so sensory signals less frequently reach the central nervous system?
It does, but it also constricts blood vessels, staunching blood flow and inhibiting swelling.

pivoxa15 said:
Also dry ice such as CO2 is able to 'burn' skin because of its very low temperture, not through any chemical effect. It has been used in the past by doctors to remove warts and even small skin cancers. How does dry ice 'burn' skin? How does it remove what they claim is it the burning effect?
The cold freezes all the water in the cells, causing them to burst and die. Nitrogen is faster, meaning it's more effective and easier to "focus" the effect ( i.e. avoid collateral damage to surrounding tissues).
 
There is another application of cold: to prevent hair-loss during chemotherapy. A cold-cap is applied to the scalp, the cold constricts the bloodvessels so that the chemotherapeutic agent is unable to access that area and can thus not kill off the dividing cells of the hair follicle. A drawback is that metastases might escape treatment if they are located in the cold area, so it is not always used.
 
DaveC426913 said:
It does, but it also constricts blood vessels, staunching blood flow and inhibiting swelling.

So the ice pack is more of a short term thing. To prevent the kids from cying too much.


DaveC426913 said:
The cold freezes all the water in the cells, causing them to burst and die. Nitrogen is faster, meaning it's more effective and easier to "focus" the effect ( i.e. avoid collateral damage to surrounding tissues).

Is that what causes the burning sensation - cells bursting due to expansion of liquid when frozen.

We usually talk about burning when putting our hand into the fire. Does the fire also burn our cells and when they burst we get the burning sensation? Its just that we are more use to being burned by hottness than coldness that we associate burn with hot.
 
Why am I getting a sense of deja vu? Haven't we had this convo before?
pivoxa15 said:
So the ice pack is more of a short term thing. To prevent the kids from cying too much.
Partly, but it also prevents further damage.


pivoxa15 said:
Is that what causes the burning sensation - cells bursting due to expansion of liquid when frozen.

We usually talk about burning when putting our hand into the fire. Does the fire also burn our cells and when they burst we get the burning sensation? Its just that we are more use to being burned by hottness than coldness that we associate burn with hot.
Well, anything that stimulates the nerves will cause our brain to feel that sensation. Heat and cold are somehwat linked. I think one gets to the brain faster, masking the other one.

Note: our brains do not actually know what really happens, they can only know what the nerves tell them, and those messages can be fiddled with (which is why acupuncture works. You don't HAVE to stimalate the nerve at its end, say, in your finger. If you could isolate the nerve that runs to your finger, and stimulate it in your armpit, your brain thinks your finger has been poked.)
 
pivoxa15 said:
So the ice pack is more of a short term thing. To prevent the kids from cying too much.
The reduction in swelling also reduces the amount of injury to surrounding tissue so it will heal faster.

Is that what causes the burning sensation - cells bursting due to expansion of liquid when frozen.

We usually talk about burning when putting our hand into the fire. Does the fire also burn our cells and when they burst we get the burning sensation? Its just that we are more use to being burned by hottness than coldness that we associate burn with hot.

That "burning" sensation isn't associated with temperature sensation, but is a pain sensation. It doesn't matter if it's caused by hot or cold or a cut, it's all the same "stinging" feeling.
 
Moonbear said:
The reduction in swelling also reduces the amount of injury to surrounding tissue so it will heal faster.

How does the ice pack reduce swelling?


Moonbear said:
That "burning" sensation isn't associated with temperature sensation, but is a pain sensation. It doesn't matter if it's caused by hot or cold or a cut, it's all the same "stinging" feeling.

Ok. And the pain sensation is due to the bursting or damage of cells?
 
pivoxa15 said:
How does the ice pack reduce swelling?
When you injure yourself, you get a local dilation of the bloodvessels as a response to the injury. This will lead to an increased bloodflow to the area, causing redness and warmth.
At the same time the bloodvessels locally permeabilize so that the increased number of passing leukocytes can pass the bloodvessel wall and enter the injured tissue to start the healing process. The white blood cells will release cytokines, that will attracts additional cells. The permeabilization increases the passage of plasma into the tissue, causing swelling. Pain results from the swelling and probably other factors.

So, an icepack will cause the contraction the dilating bloodcells, thereby the circulation in the area is reduced, there won't be enough circulating white bloodcells to start an inflammation reaction -> reduced swelling.