# Why do sunburns take a while to hurt? **URL:** \ **Category:** Factual Questions\ **Created:** [September 28, 2025, 1:27am UTC](https://boards.straightdope.com/t/why-do-sunburns-take-a-while-to-hurt/1023446 "2025-09-28T01:27:52Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Nars\_Glinley](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nars_glinley/32/8177_2.png) [@Nars\_Glinley](https://boards.straightdope.com/u/Nars_Glinley)\ **Post date:** [September 28, 2025, 1:27am UTC](https://boards.straightdope.com/t/why-do-sunburns-take-a-while-to-hurt/1023446/1 "2025-09-28T01:27:52Z")
Anyone that’s had a sunburn knows that the pain gets worse hours after the sun exposure. Why does it take so long for the body to feel the pain? ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [September 28, 2025, 11:31am UTC](https://boards.straightdope.com/t/why-do-sunburns-take-a-while-to-hurt/1023446/2 "2025-09-28T11:31:48Z")
Because the redness and pain are actually part of your body’s _reaction_ to the damage caused to your skin cells by UV rays. It takes a few hours before the healing process to rev up. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [September 28, 2025, 2:35pm UTC](https://boards.straightdope.com/t/why-do-sunburns-take-a-while-to-hurt/1023446/3 "2025-09-28T14:35:28Z")
Further, what we call sunburn is inflammation and not a thermal burn. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [September 28, 2025, 2:44pm UTC](https://boards.straightdope.com/t/why-do-sunburns-take-a-while-to-hurt/1023446/4 "2025-09-28T14:44:46Z")
Even [acute radiation sickness](https://en.wikipedia.org/wiki/Acute_radiation_syndrome) (caused by ionizing radiation) does not kick in _immediately_. ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [September 28, 2025, 3:53pm UTC](https://boards.straightdope.com/t/why-do-sunburns-take-a-while-to-hurt/1023446/5 "2025-09-28T15:53:37Z")
Technically, sunburn is just that: shallow ionizing radiation tissue damage. (The difference between ultraviolet and gamma is just a few orders of magnitude of electromagnetic frequency.) ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [October 4, 2025, 2:32am UTC](https://boards.straightdope.com/t/why-do-sunburns-take-a-while-to-hurt/1023446/6 "2025-10-04T02:32:03Z")
My understanding is that pain induction in sunburn involves the action of peptides like COX-2 (causes cell proliferation and prostaglandin release) and CXCL5, which mediate inflammation and pain response, but take time to be released in quantity in the area of acute solar damage, and manifest later than erythema (redness) which appears within a few hours. Complex stuff. > **[Why Do Sunburns Hurt Anyway?](https://www.utmb.edu/mdnews/podcast/episode/why-do-sunburns-hurt-anyway)** > > Ever wondered why sunburns hurt so much? Well, researchers believe that the pain may be the doing of a molecule called CXCL5, which seems to control sensitivity to pain from UVB radiation. You may recall that the sun emits UVA, UVB and UVC rays. UVC... > [@jnglmassiv](#): > > Further, what we call sunburn is inflammation and not a thermal burn. Inflammation certainly occurs in response to sunburn, but there’s also histologic damage to epidermal layers in acute sunburn evident by vacuolated and shrunken keratinocytes - not entirely different from thermal burns. And at further risk of being a pissant, I will note that there _can_ be immediate effects of a large enough dose of ionizing radiation, i.e. the sudden vomiting experienced by a victim of a fatal “demon core” nuclear accident in the 1940s. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [October 4, 2025, 4:41pm UTC](https://boards.straightdope.com/t/why-do-sunburns-take-a-while-to-hurt/1023446/7 "2025-10-04T16:41:18Z")
It is true that in the event of a criticality accident nausea and a burning sensation can occur within seconds. The pink colour associated to cutaneous radiation syndrome seem to have shown up within five to ten minutes e.g. in the case of Cecil Kelley, if this report is accurate: [https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-95-4005-11](https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-95-4005-11) . Both gamma rays and neutrons were involved, in this case. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [October 8, 2025, 5:12am UTC](https://boards.straightdope.com/t/why-do-sunburns-take-a-while-to-hurt/1023446/8 "2025-10-08T05:12:54Z")
> [@jnglmassiv](#): > > Further, what we call sunburn is inflammation and not a thermal burn. The acute inflammation phase can be prevented by the use of an anti-inflamatory drug. Asprin. You have to take the asprin before the sunburn starts to hurt. My doctor warned me that this is not an excuse for allowing yourself to be sunburned. You still get the other damage, and the skin cancer is the result of tanning, which happens even if your sunburn doesn’t hurt. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [October 8, 2025, 2:18pm UTC](https://boards.straightdope.com/t/why-do-sunburns-take-a-while-to-hurt/1023446/9 "2025-10-08T14:18:08Z")
> [@Melbourne](#): > > The acute inflammation phase can be prevented by the use of an anti-inflamatory drug. Asprin. You have to take the asprin before the sunburn starts to hurt. I was ready to publicly doubt that ‘one simple trick’ but I’m glad I took a little extra time to research before posting my accusatory reply! There _does_ seem to be evidence asprin has preventative properties for sunburn I wasn’t aware of. Anecdotally, I’ve perceived fewer minor sunburns lately and now wonder if it’s since starting a daily baby asprin (81 mg, doc’s orders) about 2 years ago. The slight tender reddness 12 hours after lawn mowing or frisbee golf is less of a certainty than in years past. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [October 8, 2025, 2:45pm UTC](https://boards.straightdope.com/t/why-do-sunburns-take-a-while-to-hurt/1023446/10 "2025-10-08T14:45:13Z")
> [@gnoitall](#): > > Technically, sunburn is just that: shallow ionizing radiation tissue damage. (The difference between ultraviolet and gamma is just a few orders of magnitude of electromagnetic frequency.) But those few orders of magnitude are the difference between [_ionizing_ radiation](https://en.wikipedia.org/wiki/Ionizing_radiation) due to gammas (and X-rays) and _non-ionizing_ radiation caused by the UV that can penetrate the atmosphere and cause sunburns. While very high-frequency UV is indeed considered to be ionizing radiation, most of these frequencies are absorbed by the atmosphere. Were this not the case, the surface of the Earth would be sterilized. In other words, I don’t believe it’s correct to refer to a sunburn as “shallow _ionizing_ radiation tissue damage.” While that would indeed be a good description for exposure to beta particles (though these are actually discrete particles, not electromagnetic radiation), the UV that reaches the ground and causes sunburns has a low enough frequency and energy to be considered non-ionizing radiation.