Going outside on a clear summer day is a good reminder that the sun is indeed a blazing fireball of unfathomable heat. Even from 94.486 million miles away, you can feel the ultraviolet rays from that enormous star beaming against your delicate skin. You may even feel them to such a degree that you get to thinking, “Hey, I can feel myself getting sunburned right now, so I should probably apply some sunscreen.” Chances are, though, you already have a sunburn if you can feel your skin burning.
“Sometimes you can feel yourself getting too much UV exposure,” explains dermatologist Anthony Rossi. “But by the time you feel the sunburn, it’s usually too late, because the damage has already been done. The reason why there’s a delay is because the UV-induced burn releases inflammatory cells and mediators, which signal pain that occurs later.”
This is also why you normally turn red and feel the full brunt of your burn hours after being out in the sun: That redness is actually the result of increased blood flow bringing immune cells to the already-burned skin to help clear things up. This increased blood flow is also what causes your skin to feel warm after a sunburn, which again only occurs hours after the burn itself.
Importantly, all of this happens — the burning, the reddening and the healing — at different rates for different people. “This is different for different people, depending on their skin type,” Rossi reiterates. “This is the same for the time it takes people to actually burn, which is called MED (medium erythema dosage). Each person’s MED is different, depending on their skin type and how much melanin they have.”
Therefore, if you think you can feel yourself beginning to burn, you already got burned, buddy.