system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5Why does it take so long for a sunburn to hurt/ appear after the burn is inflicted?
gpt
Ok, so...

Sunburn isn't like a burn from, say, grabbing a hot piece of metal--it's an ionizing radiation burn, caused by ultraviolet radiation.

Like other forms of ionizing radiation, UV radiation doesn't directly stimulate or damage pain nerves like heat does.  As one other commenter stated, it damages RNA, which later causes inflammation.  It's the inflammation that eventually causes the pain.