Sunburn
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- For information on the Florida regional Burning Man event, see SunBurn. For information about the anti-ship missiles, see SS-N-22 Sunburn.
A sunburn is a burn to the skin produced by overexposure to ultraviolet (UV) radiation, commonly from the sun's rays. A similar burn can be produced by overexposure to other sources of UV such as from tanning lamps, or occupationally, such as from welding arcs. Exposure of the skin to lesser amounts of UV will often produce a suntan.
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Development and consequences
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 that sunburn can occur in less than 15 minutes. [1]
Nevertheless, the inflicted harm is often not immediately obvious. After being burned, skin may turn red 2 to 6 hours later. Pain is worst 6 to 48 hours afterward. The burn continues to develop for 24 to 72 hours after exposure. Skin peeling begins 3 to 8 days after the burn occurs. Common outcomes include tenderness, pain, edema, red and/or peeling skin, rash, nausea and fever. Sunburns may be first- or second-degree burns.
Minor sunburns typically cause nothing more than slight redness and tenderness to the affected area. 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. 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.
Increased risk
[[Image:NOAA_UV- source: NOAA]] The risk of sunburn increases with proximity to the earth's equator. It can also be increased by pharmaceutical products that sensitise some people taking them to UV radiation. Certain antibiotics, contraceptives, and tranquillizers have this effect.
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 increases in sunburn incidences and in solarium popularity as individuals attempt to tan.
In recent years, the incidence and severity of sunburn has increased worldwide, especially in the southern hemisphere, because of damage to the ozone layer due to CFCs. Some are worried that ozone depletion and the seasonal ozone hole has led to dangerously high levels of UV radiation.
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.
Protection
It is advisable to wear long-sleeved garments and wide-brimmed hats or use an umbrella when in the sun. Minimisation of sun exposure between the hours of 10 am to 3 pm 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.
Sunscreen should have a SPF rating of at least 15. It should be applied half an hour before going out and reapplied every two hours thereafter.
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.
When one is exposed to any artificial source of occupational UV, special protective clothing (for example, welding masks) should be worn.
Treatment
There are numerous topical skin products that can relieve the pain of a sunburn and speed up the healing process. However, it is best never to cover a sunburn that is blistered or open with any sort of cream, gel, or ointment as it may cause the wound to become infected.
The symptoms of milder sunburn can be treated with an antipruritic such as Calamine Lotion.
The thick mucilaginous gel on an Aloe vera plant or aloe-based products are popular treatments that heal the burn and relieve pain.
Regular white vinegar and apple cider vinegar have often been touted for their usefulness in treating sunburns and preventing blistering and peeling.
Other common folk remedies involve the application of lavender oil, tea (cooled), yogurt, St. John's wort, or cucumbers to the burnt skin.
Skin treatments aside, the pain from a sunburn is often best treated with an analgesic such as acetaminophen or ibuprofen. Additional relief may be found by putting a cool, wet towel over the affected area.
Using tomato on the skin is a more painful way of treating the burn, but is mostly effective.
Ice provides immediate relief; however, once removed, discomfort may follow. Also of note is the common use of almond milk which is particularly soothing to children. Avocado-based moisturing lotions have proven as effective as standard pharmaceutical aftersun treatments in cooling the burn, reducing the edema and restoring elasticity to the burnt skin if applied within 24 hours of the burn.
A hot shower may also take the sting and the heat out of mild sunburn however there is significant risk with severe sunburn that a hot shower will increase the damage perhaps leading to blistering of skin which has not yet blistered.
Windburn
On cold days, people often refer to their sunburn as a windburn. Windburn is actually a distinct condition whereby the top layer of oil is removed from the skin, causing excessive dryness that leads to redness and a burning feeling. However, people commonly believe that any burn on a cold day is windburn. In fact, since sunburn is a result of UV light rather than heat, hot temperatures are not necessary. This mistake is frequently made while skiing, where sunburn can occur in very cold temperatures since the UV light is reflecting off the snow and higher altitudes provide less atmosphere to block UV.
Animals
Many animals can also suffer from sunburn, however most are protected by a layer of dense fur. Despite myths stating that only hippopotami and pigs can be affected by sunburn, almost all animals, given the right situation can - even fish can suffer sunburn (though pigs and hippopotami are more prone due to their hairless skin producing less oil - a natural sun protector).
See also
- Sun unit unit of weighted sun intensity
- Hyperthermia (heat stroke) is another health hazard resulting from excessive exposure to the sun.
External links
- Avoid sunburn, calculate protection time online
- Sun Protection Tips
- Protecting Kids from the Sun
- Sunburn Information
- Sunburn Pictures
- Medline - Sunburn
- Medline - Sunburn First Aid
- Sunsmart Victoria (Australia)
- Influences of Ozone Depletion on Human and Animal Health
References
- 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. Proc Natl Acad Sci. 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. J Invest Dermatol. 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? J Invest Dermatol. Oct 2003;121(4):862-8.
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