A sunburn is a radiation burn, specifically caused by ultraviolet (UV) radiation from the sun. In terms of severity, most sunburns are first-degree burns, meaning they affect only the outermost layer of skin. More intense sun exposure can produce a second-degree burn with blistering that reaches deeper tissue.
Why Sunburn Is a Radiation Burn
Unlike a thermal burn from touching a hot pan or a chemical burn from an acid, a sunburn is caused by UV radiation penetrating your skin cells. UVB rays are the primary culprit. They fracture and tangle small structures inside your cells called micro-RNA. When that happens, the damaged cells release the altered RNA, which signals neighboring healthy cells to trigger inflammation. That inflammation is what produces the redness, heat, and pain you recognize as sunburn. It’s your body’s way of clearing out cells with damaged DNA so healing can begin.
This makes sunburn fundamentally different from other common burns, even though the end result (red, painful, possibly blistered skin) can look similar.
First-Degree vs. Second-Degree Sunburn
Most sunburns are first-degree burns. They affect only the epidermis, the thin outer layer of your skin. You’ll see redness, feel tenderness, and the skin may be warm to the touch, but there are no blisters.
A more severe sunburn crosses into second-degree territory. These burns damage the epidermis and part of the dermis, the thicker layer beneath it. The hallmark of a second-degree sunburn is blistering. The skin may also swell significantly, and the pain is considerably worse. Second-degree sunburns take longer to heal and carry a higher risk of infection, especially if blisters break open.
Third-degree sunburns are extremely rare but not impossible, particularly at high altitude or near reflective surfaces like water and sand, where UV exposure intensifies.
How Sunburn Develops Over Time
Sunburn doesn’t show up the moment you step out of the sun. Pain typically starts within a few hours of exposure. Redness deepens progressively, with pain peaking around 24 hours after the burn. Over the following week or so, the damaged skin peels as your body sheds the injured cells, and color gradually returns to normal.
This delayed onset catches many people off guard. You can feel fine at the beach and not realize the severity until that evening or the next morning, by which point the damage is already done.
When Sunburn Becomes Sun Poisoning
A severe sunburn can trigger systemic symptoms that go beyond skin damage, sometimes called sun poisoning. This isn’t a separate condition so much as a sunburn that’s severe enough to affect your whole body. Signs include fever, chills, headache, nausea, dizziness, confusion, and extreme thirst. Much of this is driven by dehydration, which compounds the inflammatory stress your body is already under.
If you’re shivering, vomiting, feeling faint, or confused after heavy sun exposure, that’s a sign your body is struggling to cope with the damage and fluid loss.
Treating a Sunburn at Home
For a typical first-degree sunburn, cooling the skin is the first step. Apply a clean towel dampened with cool tap water for about 10 minutes, several times a day. A cool bath with about 2 ounces of baking soda can also help. Follow up with aloe vera gel or calamine lotion, and consider chilling the product in the refrigerator beforehand for extra relief.
Take ibuprofen or acetaminophen as soon as possible after you notice the burn. Anti-inflammatory pain relievers work best when taken early, before the inflammatory response fully ramps up.
One thing to avoid: topical products ending in “-caine,” like benzocaine. These numbing creams can irritate already damaged skin and have been linked to a rare but serious condition that reduces the oxygen-carrying capacity of your blood.
If You Have Blisters
Leave intact blisters alone. They act as a natural bandage, protecting the raw skin underneath while it heals. If a blister breaks on its own, trim the dead skin with clean, small scissors, wash gently with mild soap and water, apply antibiotic ointment, and cover the area with a nonstick bandage to prevent infection.
Long-Term Skin Cancer Risk
Every sunburn, regardless of how mild it seems, involves UV-induced DNA damage. Over time, this accumulates. A meta-analysis cited by Cancer Research UK found that melanoma risk is roughly three times higher in people who have been sunburned once every two years (about 10 times per decade) compared to those who have never been sunburned. For women who experienced 26 or more painful or severe sunburns over their lifetime, the risk was two to three times higher.
Importantly, this risk increase applies whether the sunburns happened in childhood or adulthood. The old idea that only childhood sunburns “count” toward cancer risk isn’t supported by the data. Every blistering burn matters, at any age.