Why/How does sun-burnt skin retain so much heat?

Factual Questions
1

Why/How does sun-burnt skin retain so much heat, ever several days after the burn?

Thanks

2

I don’t think it’s retaining heat. I think what you’re feeling is the heat generated by your body’s defenses as they struggle to repair the damage and fight off infection. Blood flow to the damaged area is increased dramatically.

3

Yup. Since the area is damaged your body increases blood flow to the area, which makes a localized increase in body heat.

4

Right. I also suspect the redness of early sunburn is from the blood flow, though don’t know this - anyone know?

5

That appears to be true: http://www.newton.dep.anl.gov/askasci/bio99/bio99233.htm

6

Yep. There’s a simple way to demonstrate this – if you press the sunburned skin you can squeeze out the blood temporarily. On a person with sufficiently light skin, this is pretty obvious, and you can leave hand prints or draw pictures (as long as they’ll let you…).

7

Sunburns feel hot because the skin is relatively hot when compared with its typical normal. As mentioned above, this is because the injury to the skin increases the blood flow, raising the skin temperature.

Ordinarily your skin temperature is close to about 90 degrees or so. This varies markedly according to which part of the skin you measure and what the ambient temperature is right next to that area of skin, of course. When the blood supply to the skin is increased, the temperature of the skin becomes closer to the temperature of blood–closer to 99 degrees or so. With enough sunburn, inflammatory reactions can elevate the whole body temperature as well, making the skin also hotter than 99 degrees. Finally, injury to the skin renders it much more sensitive, increasing the perception that it’s hot–increasing, in effect, the sensitivity of all skin receptors.

8

Yep, it’s the inflammatory response causing greater bloodflow, from what I understand. My daughters both got sunburned yesterday, and their shoulders feel like they’re absolutely on fire compared to the rest of their skin. I took our ear thermometer last night and demonstrated to them that it wasn’t just an illusion; the rest of their skin is cooler than 91 degrees Fahrenheit (the lowest temperature the ear-mometer can register), but their burned shoulders are 96.5 degrees. It was fascinating.

9

You’re the coolest! :smiley: (Pun unintended.)