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A sunburnt back that was partially protected by a bathing suit top.
A sunburn is a form of suntan.
Excessive UV radiation is the leading cause of primarily non-malignant skin indirect DNA damage if the damage is not properly repaired. Proper repair occurs in the majority of DNA damage. The only cure for sunburn is slow healing, although some skin creams can help with the symptoms.
Sunburn is caused by UV radiation, either from the sun or from artificial sources, such as free radicals, thus indirect DNA damage.
Experiments with mice found that protection against sunburn by chemical sunscreens does not necessarily provide protection against other damaging effects of UV radiation such as enhanced melanoma growth.
 Sunburn and skin cancer
Ultraviolet B (UVB) radiation causes dangerous sunburns and increases the risk of two types of skin cancer: 
Some exposure to sunlight is not only harmless but positively necessary to health. Humans need vitamin D; most is synthesised in the body by exposure of the skin to sunlight, with some from the diet. People with darker skins need more sunlight to maintain vitamin D levels. The widespread concern about over-exposure to the sun causing cancer has led some people to go too far in avoiding exposure and using sunscreen; this can lead to vitamin D deficiency and the condition of rickets due to this deficiency, particularly in children, and particularly in climates with less sunshine. Cases of rickets are, indeed, on the increase. Twenty to thirty minutes of unimpeded exposure to the sun two to three times a week are recommended.
 Controversy over sunscreen
The statement sunburn causes skin cancer is considered accurate when it refers to either basal-cell carcinoma, the mildest form of cancer, or squamous cell carcinoma. However, this may be misleading when it comes to malignant melanoma (see picture: UVR sunburn melanoma). The statistical correlation between sunburn and melanoma is assumed to be due to a common cause — UV radiation. Instead, this correlation may be generated via different mechanisms. Direct DNA damage is ascribed by many medical doctors to a change in behaviour of the sunscreen user due to a false sense of security afforded by the sunscreen. While some researchers believe that these confounding factors can be controlled for effectively, others believe there to be insufficient correction for light-skinned individuals and indirect DNA damage.[clarification needed]
Exposure to UV rays generates  Whether sunscreen prevents or promotes the development of melanoma depends on the relative importance of the protective effect from the topical sunscreen versus the harmful effects of the absorbed sunscreen.
The use of sunscreen is known to prevent the direct DNA damage that causes sunburn and the two most common forms of skin cancer, basal-cell carcinoma and squamous cell carcinoma.
 Other risk factors
Because of variations in the intensity of UV radiation passing through the atmosphere, the risk of sunburn increases with proximity to the noon, when shadows are at their minimum and the sun's radiation passes more directly through the atmosphere. Regardless of one's latitude (assuming no other variables), equal shadow lengths mean equal amounts of UV radiation.
 Pharmaceutical products
Sunburn can also be caused by 
 Ozone depletion
In recent years, the incidence and severity of sunburn has increased worldwide, especially in the southern hemisphere, because of damage to the 
 Popularity of tanning
Suntans, which naturally develop in some individuals as a protective mechanism against the sun, are viewed by many in the Western world as desirable. This has led to increased exposure to UV radiation from both the natural sun and solaria.
Typically there is initial redness (pain, proportional in severity to both the duration and intensity of exposure.
Other symptoms are burns.
One should immediately speak to a dermatologist if one develops a skin lesion that has an asymmetrical form, has darker edges than center, changes color, or becomes larger than 1/4 inch (6 mm). (see Melanoma)
Minor sunburns typically cause nothing more than slight redness and tenderness to the affected areas. In more serious cases, blistering can occur. Extreme sunburns can be painful to the point of debilitation and may require hospital care.
Sunburn can occur in less than 15 minutes, and in seconds when exposed to non-shielded welding arcs or other sources of intense ultraviolet light. Nevertheless, the inflicted harm is often not immediately obvious.
After the exposure, skin may turn red in as little as 30 minutes but most often takes 2 to 6 hours. Pain is usually most extreme 6 to 48 hours after exposure. The burn continues to develop for 24 to 72 hours, occasionally followed by peeling skin in 3 to 8 days. Some peeling and itching may continue for several weeks.
Long-term low-intensity exposure to sunlight is known to cause significant ageing of the skin; other health effects are not accurately known. A particular example with very noticeable ageing is that of a 69-year-old truck driver in Chicago, USA who drove in the city for 28 years. A photograph of his face Window glass does not absorb UVA, which can penetrate the epidermis and upper layers of dermis. Chronic UVA exposure can cause photoageing: thickening of the epidermis and stratum corneum and destruction of elastic fibers; it can cause DNA mutations and toxicity which can lead to cancer, although less carcinogenic than UVB.
One of the most effective ways to prevent sunburn is to reduce the amount of UV radiation reaching the skin. The strength of sunlight is published in many locations as a UV index. The World Health Organization recommends to limit time in the midday sun (between 10 a.m. and 4 p.m.), to watch the UV index, to seek shade, to wear protective clothing and a wide-brim hat, and to use sunscreen. Sunlight is generally strongest when the sun is close to the highest point in the sky. Due to time zones and daylight saving time, this is not necessarily at 12 p.m., but often one to two hours later.
Commercial preparations are available that block UV light, known as sunscreens or sunblocks. They have a sunburn protection factor (SPF) rating, based on the sunblock's ability to suppress sunburn: The higher the SPF rating the lower the amount of direct DNA damage.
A sunscreen rated as SPF 10 blocks 90% of the sunburn-causing UVB radiation; an SPF20-rated sunscreen blocks 95%[μl of sunscreen is applied per square cm of exposed skin. This translates into about 28 ml (1 oz) to cover the whole body of an adult male, which is much more than many people use in practice. Although UVA radiation does not cause sunburn, it does contribute to skin aging and an increased risk of skin cancer. Many sunscreens provide broad-spectrum protection, meaning that they protect against both UVA and UVB radiation.
Research has shown that the best protection is achieved by application 15 to 30 minutes before exposure, followed by one reapplication 15 to 30 minutes after exposure begins. Further reapplication is necessary only after activities such as swimming, sweating, and rubbing. This varies based on the indications and protection shown on the label — from as little as 80 minutes in water to a few hours, depending on the product selected.
When one is exposed to any artificial source of occupational UV, special protective clothing (for example, welding helmets/shields) should be worn.
There is also evidence that common foods may have some protective ability against sunburn if taken for a period before the exposure.flavonoids has also been found to have a similar effect if eaten for long periods before exposure.
The eyes are also sensitive to sun exposure. Wrap-around freckles, are often found within the iris.
Dietary factors influence susceptibility to sunburn, recovery from sunburn, and risk of secondary complications from sunburn. Several dietary 
Sunburn increases the metabolic demands on the body, increasing the needs for water and other nutrients to prevent skin breakdown and secondary infections.
The most important aspects of sunburn care are to avoid 
 See also
- Sun unit
- Hyperthermia (heat stroke)
- List of cutaneous conditions
- Potential health risks of sunscreen
- J. M. Dawes, M. Calvo, J. R. Perkins, K. J. Paterson, H. Kiesewetter, C. Hobbs, T. K. Y. Kaan, C.Orengo, D. L.H. Bennett, S. B.McMahon, CXCL5 Mediates UVB Irradiation–Induced Pain. Sci. Transl. Med. 3, 90ra60 (2011). http://dx.doi.org/10.1126/scitranslmed.3002193
- guardian newspaper: Rickets warning from doctors as vitamin D deficiency widens, 22 January 2010
- Health Report – 13/09/99: Skin Cancer and Sunscreen
- “Avoiding Sun-Related Skin Damage” – No longer available
- Sunburn-Topic Overview
- Al Gore, “Earth in the Balance, Ecology and the Human Spirit”‘, 1992
- Healthwise Incorporated (March 27). “Suntan”. http://www.webmd.com/hw/health_guide_atoz/sts15336.asp?navbar=hw82391. Retrieved August 26, 2006.
- Sun protection. World Health Organization.
- Pullen, Richard L. et. al., “Danger! Severe sunburn in season”, Nursing Made Incredibly Easy!, July/August 2011 – Volume 9 – Issue 4 – p 13–15.
- </ref Calamine lotion can also help reduce skin irritation due to mild sunburn.
- Agar NS, Halliday GM, Barnetson RS, Ananthaswamy HN, Wheeler M, Jones AM (2004). “The basal layer in human squamous tumors harbors more UVA than UVB fingerprint mutations: a role for UVA in human skin carcinogenesis”. Proc. Natl. Acad. Sci. U.S.A. 101 (14): 4954–9. 15041750. //www.ncbi.nlm.nih.gov/pmc/articles/PMC387355/.
- Baron ED, Fourtanier A, Compan D, Medaisko C, Cooper KD, Stevens SR (2003). “High ultraviolet A protection affords greater immune protection confirming that ultraviolet A contributes to photoimmunosuppression in humans”. J. Invest. Dermatol. 121 (4): 869–75. doi:10.1046/j.1523-1747.2003.12485.x. PMID 14632207.
- Hall HI, Saraiya M, Thompson T, Hartman A, Glanz K, Rimer B (2003). “Correlates of sunburn experiences among U.S. adults: results of the 2000 National Health Interview Survey”. Public Health Rep 118 (6): 540–9. 14563911. //www.ncbi.nlm.nih.gov/pmc/articles/PMC1497591/.
- Haywood R, Wardman P, Sanders R, Linge C (2003). “Sunscreens inadequately protect against ultraviolet-A-induced free radicals in skin: implications for skin aging and melanoma?”. J. Invest. Dermatol. 121 (4): 862–8. doi:10.1046/j.1523-1747.2003.12498.x. PMID 14632206.
- NOAA UV-Index Summary with Data Graphs
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