Scientifically/ chemically (?) how does this work?

Question

ok. so you put an ice cube on your skin enough so it gets wet, then put salt on the wet spot, and set the ice cube on top of the salt. & it burns your skin pretty bad. (i believe it's a burn - feels like one, and is swollen and red).

How does that work?

And how long does the "burn" stick around?

Answer 1

look at the question:

"Why does it burn your hand when you put salt then ice on it?"

(this tells what happens and how)

someone has said that their burn lasted about ten days and then they had a scar for about 2 months

Answer 2

Part of the problem is that salt water can achieve a much lower temperature than pure water without freezing.  That's why you put rock salt in the ice pack around an ice cream maker -- you are taking advantage of Raoult's Law of Freezing Point Depression.  The same effect is what you experience when you use salt or "Snow Melt" to clear your driveway or sidewalk, even when the temperatures are below freezing.

And while your body can pretty well respond and counteract the near-freezing of the cells under the plain ice, the significantly colder temperature of the salt water, coupled with the osmotic effect of the salt solution, cause much more damage to the skin, resulting in the nastier burn.