Sunburn
A radiation burn from UV overexposure causing inflammation and skin damage.
Sunburn is a type of radiation burn that damages living tissue, most often the skin, when it gets too much ultraviolet (UV) radiation, typically from the Sun. The body’s inflammatory response kicks in because UV radiation harms nucleic acids—specifically, UVB rays damage DNA, which sets off a chain reaction leading to redness, pain, and swelling. This condition is a major cause of non-malignant skin tumors and raises the risk of three skin cancers: melanoma, basal-cell carcinoma, and squamous-cell carcinoma.
**Signs and symptoms** The first signs are redness (erythema) and swelling, which vary with how much UV exposure someone got. Severe cases can bring blistering, itching, peeling, rash, nausea, fever, chills, and fainting—sometimes called sun poisoning. The affected skin feels warm because capillaries near the surface release heat. Sunburns range from superficial (first-degree) to partial-thickness (second-degree) burns; blistering signals a second-degree burn.
**Variations** Minor sunburns cause only slight redness and tenderness. More serious ones involve blistering. Extreme burns can be so painful they become debilitating and may need hospital care.
**Duration** Sunburn can happen in under 15 minutes of sun exposure, though the first signs may not show for a few hours. With intense UV sources like welding arcs, it can occur in seconds. Symptoms peak 24 to 36 hours after exposure and usually start improving after 3 to 5 days. Skin may flake and peel after a few days, with full healing typically within 7 days; small amounts of peeling can continue for days or weeks.
**Skin cancer** UV radiation causes sunburns and increases the risk of melanoma, basal-cell carcinoma, and squamous-cell carcinoma. The risk of melanoma rises in direct proportion to a person’s total number of sunburns over a lifetime. In the United States and Australia, regular sunscreen use could prevent about one-third of melanomas.
**Mechanism** Sunburn comes from prolonged UV exposure from the Sun or artificial sources like tanning lamps, welding arcs, or germicidal UV lights. Two types of UV reach Earth’s surface: UVA and UVB. UVA is 1,000 to 2,000 times less effective at causing sunburn than UVB, because it carries less energy. UVB damages DNA directly, triggering a stress response that leads to inflammation and immune cell recruitment.
Quick Facts
- Field
- Dermatology
- Complications
- Skin cancer
- Risks
- Working outdoors, skin unprotected by clothes or sunscreen, skin type, age, albinism
- Prevention
- Use of sunscreen, wearing sun protective clothing
Facts from the source article.
Lore & Background
Sunburn results from prolonged exposure to ultraviolet radiation from the Sun or artificial sources like tanning lamps and welding arcs. Two types of UV reach Earth's surface: UVA and UVB, with UVB being 1,000–2,000 times more effective at causing sunburn. UVB damages DNA directly, triggering a stress response that leads to inflammation and immune cell recruitment. DNA damage, not RNA damage, is the direct cause of acute sunburn. The body responds with DNA repair, apoptosis, peeling, and increased melanin production.
Reader's Guide
Sunburn is a significant public health concern due to its link to skin cancer, including melanoma, basal-cell carcinoma, and squamous-cell carcinoma. The risk of melanoma increases dose-dependently with cumulative sunburn episodes, and an estimated one-third of melanomas in the United States and Australia could be prevented with regular sunscreen use. Sun protective measures like sunscreen and sun protective clothing are widely accepted to prevent sunburn and some types of skin cancer. Special populations, including children, are especially susceptible. The UV Index helps assess risk, with factors such as time of day (10 am to 4 pm), cloud cover, reflective surfaces, season, altitude, and latitude influencing exposure. Fitzpatrick's skin phototype system classifies susceptibility, with lighter skin types (I and II) burning most easily, though all skin types can develop sunburn or skin cancer. Suntans provide only modest protection (SPF 3) and are viewed as desirable in the Western world, leading to increased UV exposure.
Did You Know?
- Sunburn can occur in less than 15 minutes of sun exposure, but first signs may not appear for a few hours.
- UVB damages mRNA, triggering inflammation via the ZAK-alpha protein, while UVA is 1,000–2,000 times less effective at causing sunburn.
- The pain of sunburn may be caused by overproduction of the protein CXCL5, which activates nerve fibers.
- Melanin absorbs UV light, but human melanocytes contain over 2,000 genomic sites that are up to 170-fold more sensitive to UV induction of cyclobutane pyrimidine dimers.
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