Queimadura solar: diferenças entre revisões
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Revisão das 04h10min de 3 de janeiro de 2007
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Uma queimadura solar é uma queimadura na pele produzida pela superexposição à radiação ultravioleta (UV), geralmente dos raios solares. Uma queimadura semelhante pode ser produzida por uma superexposição a outras fontes de UV como lâmpadas de bronzeamento, ou occupationally, such as from welding arcs. A exposição da pele a quantidades cada vezes menores de UV frequentemente produz um bronzeamento solar. Os sintomas usuais são pele avermelhada e quente ao toque, um sentimento de a washed out feeling, and mild dizziness.
As queimaduras solares podem ameaçar a vida e são causa de muitos tipos de câncer. Elas podem ser evitadas facilmente através do uso de filtro solar, roupas (e chapéus), e com a limitação do tempo de exposição solar, especialmente durante o período do meio dia e tarde. A única cura para a queimadura da pele é a lenta recuperação, embora cremes de pele possam ajudar.
In the winter time, windburn is commonly confused with a sunburn, with typically milder symptoms.
Desenvolvimento e conseqüências
Typically there is initial redness (erythema), followed by varying degrees of pain, both proportional in severity to the duration and intensity of exposure. The condition occurs when incident UV radiation exceeds the protective capacity of melanin in the skin. Concentrations of this pigment vary greatly among individuals, but in general, darker-skinned people have more melanin than those with lighter skin. Correspondingly, the incidence of sunburn among dark-skinned individuals is lower.
UV radiation is divided into the UVA (380–315 nm), UVB (315–280 nm) and UVC (280-180 nm) sub-bands. Ozone in the Earth's atmosphere filters out a portion of this before it reaches the planet's surface. UVC is almost entirely eliminated by the atmosphere, but enough UVA and UVB penetrates it in large enough quantities that sunburn can occur in less than 15 minutes. Nevertheless, the inflicted harm is often not immediately obvious.
After the exposure, skin may turn red in 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.
Common symptoms of sunburn include tenderness, pain, edema, itching, red and/or peeling skin, rash, nausea and fever. Also, a small amount of heat is given off from the burn, giving a warm feeling to the affected area. Sunburns may be first- or second-degree burns.
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.
With respect to the spectral components of sunlight, the severity of sunburn has been found to peak in the low-frequency UVB range near the 320 nm transition to UVA. This is based on two factors:
- erythemal activity - the specific effect of different wavelengths of radiation on the skin
- solar irradiance - how much of any solar radiation wavelength can be expected to be incident on the surface of the earth
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The resulting erythemal irradiance metric is calculated by weighting measurements of solar irradiance with experimental measurements of erythemal activity. When this product is graphed, there is a peak at 308 nm.
At the cellular level, UVB light causes DNA damage which may be passed onto subsequent generations of a cell's progeny, leading to increased risk of skin cancer. Damaged cells die and release toxins which are responsible for nausea and fever. If many die, peeling may result.
The more critical and long-term danger posed by sunburn is an increased risk of future skin cancer, which is believed to be highly correlated. One incident of blistering sunburn doubles the risk of malignant melanoma [1]. But while sunburn severity gives an indication of short-term radiation over-exposure, there is also deeper penetration by UVA that occurs in the absence of perceptible symptoms. UVB was thought to be the sole causative agent in skin cancer, but there is a growing body of evidence to support the theory that both UVA and UVB are implicated.
Aumento do risco
source: NOAA
The risk of sunburn increases with proximity to the earth's equator.[1] It can also be increased by pharmaceutical products that sensitise some users to UV radiation. Certain antibiotics, contraceptives, and tranquillizers have this effect.[2] People with red hair and/or freckles generally have a greater risk of sunburn than others because of their lighter skin tone.[1]
Suntans, which naturally develop in some individuals as a protective mechanism against the sun, are viewed by many in the Western world as desirable.[3] This has led to increases in sunburn incidences and in solarium popularity as individuals attempt to tan.
A 2003 study found that 36% of US adults have a sunburn at least once a year; one study found 50% of Canadians to have been burnt in the two months prior to the study [carece de fontes].
In recent years, the incidence and severity of sunburn has increased worldwide, especially in the southern hemisphere, because of damage to the ozone layer. Ozone depletion and the seasonal ozone hole has led to dangerously high levels of UV radiation [4].
Proteção
Pele
It is advisable to consult a UV index to determine what level of protection is necessary. Potential forms of protection include wearing long-sleeved garments and wide-brimmed hats, and using an umbrella when in the sun. Minimization of sun exposure between the hours of 10 a.m. to 3 p.m. is also recommended.
Commercial preparations are available that block UV light, known as sunscreens. Sometimes called suncreams or sunblocks, they have a Sun Protection Factor (SPF) rating, based on the sunblock's ability to reduce the UVB radiation at the skin: the higher the SPF rating, the greater the protection. A sunscreen rated SPF15 blocks 93.3% UVB and an SPF30 rated sunscreen blocks 96.7%. It is best to use a broad spectrum sunscreen in order to protect against both UVA and UVB radiation. It is prudent to use waterproof formulations if one plans to engage in water-based activities. The best sunscreens attenuate UVA radiation as well UVB. Note that the stated protection factors are only correct if 2 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.
Contrary to the common advice that sunscreen should be reapplied every 2–3 hours, 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 the sun exposure begins. Further reapplication is only necessary after activities such as swimming, sweating and rubbing.[5] 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.
Another method of protection for individuals particularly concerned about sunburn is sun protective clothing. A relatively new concept in America, sun protective clothing garments are rated based on a Ultraviolet Protection Factor. Similar to the SPF rating for sunscreens, a garment rated UPF 30 blocks 96.7% UV.
When one is exposed to any artificial source of occupational UV, special protective clothing (for example, welding helmets/shields) should be worn.
Olhos
Eyes should not be neglected, and wrap-around sunglasses which block UV light should also be worn. UV light has been implicated in pterygium and cataract development.
First aid
The best treatment for most sunburns is time -- given a few weeks, they will heal.[6] Immediate, temporary relief can be obtained by putting a cool, wet towel over the affected area, or taking a cold bath or shower.[6] More severe burns may be treated with burn ointments.[6]
There are numerous topical skin products that are sold over-the-counter to relieve the pain of a sunburn. Many popular products contain aloe, aloe with Lidocane, or vitamin E. In many cases, the application of cold water or ice gives immediate but temporary relief from pain.
Some common household or folk remedies include application of white vinegar and apple cider vinegar, mustard, lavender oil, cold tea, yogurt, St. John's wort, tomatoes, almond milk, avocado, or cucumbers to the affected area or areas. These folk remedies are largely untested, and may do more harm than good. St John's wort, for example, is known to cause photosensitivity leading to increased susceptibility to sunburns in situations that would not normally cause them .[carece de fontes] Such topical treatments aside, the pain from a sunburn can be treated with an analgesic such as acetaminophen or ibuprofen.[6]
Peeling sunburns are usually accompanied by itching. Allergy medications such as Benadryl are effective at stopping the itch.[carece de fontes]
Queimadura solar em animais
Most animals can suffer from sunburn; however, many are protected by a layer of dense fur. Despite myths stating that only hippopotamuses and pigs can be affected by sunburn, almost all animals—even fish, given the right conditions—can suffer sunburn (though pigs and hippopotamuses are more prone due to their hairless skin producing less oil, a natural sun protector). The Tamworth Pig has adapted a special bristle density to minimize sunburn.
Variations in pigment, fur density, and genetic mutations such as albinism can make some individuals within the same species more or less prone to sunburn. Special care must be taken to protect individuals with variations that are more prone.
Mesmo algumas plantas, se expostas demais ao sol, podem queimar.
Veja também
- Bronzeamento solar
- Sun unit unit of weighted sun intensity
- Hyperthermia (heat stroke) is another health hazard resulting from excessive exposure to the sun.
- Windburn is often confused with a sunburn in cold weather conditions.
Referências
- Agar N, Halliday G, Barnetson R, Ananthaswamy H, Wheeler M, Jones A. The basal layer in human squamous tumors harbors more UVA than UVB fingerprint mutations: a role for UVA in human skin carcinogenesis. Proceedings of the National Academy of Sciences of the USA 6 Apr 2004;101(14):4954-9.
- Baron E, Fourtanier A, Compan D, Medaisko C, Cooper K, Stevens S. High ultraviolet A protection affords greater immune protection confirming that ultraviolet A contributes to photoimmunosuppression in humans. Journal of Investigative Dermatology Oct 2003;121(4):869-75.
- Hall H, Saraiya M, Thompson T, Hartman A, Glanz K, Rimer B. Correlates of Sunburn Experiences Among U.S. Adults: Results of the 2000 National Health Interview Survey. Public Health Reports 2003;118.
- Haywood R, Wardman P, Sanders R, Linge C. Sunscreens inadequately protect against ultraviolet-A-induced free radicals in skin: implications for skin aging and melanoma? Journal of Investigative Dermatology Oct 2003;121(4):862-8.
- ↑ a b Healthwise Incorporated (January 9, 2006). «Sunburn -- Topic Overview» Parâmetro desconhecido
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|accessyear=ignorado (|acessodata=) sugerido (ajuda); Parâmetro desconhecido|accessmonthday=ignorado (|acessodata=) sugerido (ajuda) - ↑ Healthwise Incorporated (March 27). «Suntan» Texto "accessmonthday August 26" ignorado (ajuda); Parâmetro desconhecido
|accesyear=ignorado (ajuda); Verifique data em:|data=, |ano= / |data= mismatch(ajuda) - ↑ van der Leun, J. C., and F. R. de Gruijl (1993). Influences of ozone depletion on human and animal health. Chapter 4 in UV-B radiation and ozone depletion: Effects on humans, animals, plants, microorganisms, and materials. [S.l.: s.n.] p. 95-123 Parâmetro desconhecido
|http://www.ciesin.org/docs/001-540/001-540.html=ignorado (ajuda) - ↑ Diffey, B.L. (2001). «When should sunscreen be reapplied?». J Am Acad Dermatol. 45: 882
- ↑ a b c d Heathwise Incorporated (January 9, 2006). «Sunburn -- Home Treatment» Parâmetro desconhecido
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