system
Given the following post, respond as if you're commenting on Reddit:
human
Why does scalding water sometimes feel cold?

It's usually when your hands (or whatever body part, usually an extremity) are already cold. Sometimes it's hard to gauge the temperature of running water, which kind of seems dangerous.

What's really weird is it kind of feels hot and cold at the same time, and it feels like it should hurt so that you instinctively pull away. Then you realize that it's only a feeling *akin* to pain, but isn't actually painful at all.
gpt
Very interesting subject. The reason lies in the cold-receptors of your skin, that measure cold. If you slowly increase the heat of the skin you observe this: They usually have a maximum activity when they reach 25 celsius degrees, stopping at about 30-35. A curious phenomenon, though, is that they start being activated again when the skin reaches about 40 celsius degrees. So even though your hand is scalding, your brain thinks it is quite cool. Fortunately for us, there are also heat sensors that have a maximum activety at 43 celsius. (Curiously enough, they stop at 45 degrees) This phenomenon is called an inappropriate stimulation of receptors. Another example is the stimulation of cold receptors in the mouth after eating a mint. Menthol stimulates this receptor.