Sunburn

Source: Wikipedia, the free encyclopedia.
For other uses, see Sunburn (disambiguation).

Sunburn
A sunburned neck
SpecialtyDermatology
ComplicationsSkin cancer
Risk factorsWorking outdoors, skin unprotected by clothes or sunscreen, skin type, age
PreventionUse of sunscreen, sun protective clothing
TreatmentAvoiding further exposure to the sun. Cool, frequent baths or showers for pain relief. Anti-inflammatory medications such as ibuprofen or aspirin can also help with pain. Drinking water to stay hydrated.

Sunburn is a form of

direct DNA damage by UV radiation. When the cells' DNA is overly damaged by UV radiation, type I cell-death is triggered and the tissue is replaced.[3]

Sun protective measures like sunscreen and sun protective clothing are widely accepted to prevent sunburn and some types of skin cancer.[4] Special populations, including children, are especially susceptible to sunburn and protective measures should be used to prevent damage.[5]

Signs and symptoms

Blisters on a sunburned shoulder

Typically, there is initial redness, followed by varying degrees of pain, the severity of which is proportional to the duration and intensity of sun exposure.[citation needed]

Other symptoms can include

burns. Blistering is a sign of second-degree sunburn.[6]

Variations

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.[7]

Duration

Sunburn can occur in less than 15 minutes in response to sun exposure 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.[citation needed]

After sun exposure, the skin may turn red in as little as 30 minutes, but sunburn usually takes 2 to 6 hours. Pain is usually strongest 6 to 48 hours after exposure. The burn continues to develop for 1 to 3 days, occasionally followed by peeling skin after 3 to 8 days. Some peeling and itching may continue for several weeks.[citation needed]

Skin cancer

Ultraviolet radiation causes sunburns and increases the risk of three types of skin cancer: melanoma, basal-cell carcinoma and squamous-cell carcinoma.[1][2][8] Of greatest concern is that the melanoma risk increases dose-dependently proportional to the number of a person's lifetime cumulative episodes of sunburn.[9] An estimated 1/3 of melanomas in the United States and Australia could be prevented with regular sunscreen use.[10]

Causes

dimer
(right).

Sunburn is caused by

thymine dimer. The damage is recognized by the body, which then triggers several defense mechanisms, including DNA repair to revert the damage, apoptosis and peeling to remove irreparably damaged skin cells, and increased melanin production to prevent future damage.[3]

Melanin readily absorbs UV wavelength light, acting as a photoprotectant. By preventing UV photons from disrupting chemical bonds, melanin inhibits both the direct alteration of DNA, as well as the generation of free radicals, to prevent them from indirectly damaging DNA. However, human melanocytes contain over 2,000 genomic sites that are highly sensitive to UV, and such sites can be up to 170-fold more sensitive to UV induction of cyclobutane pyrimidine dimers than the average site[11] These sensitive sites often occur at biologically significant locations near genes.

Sunburn causes an inflammation process that includes the production of prostanoids and bradykinin. These chemical compounds increase sensitivity to heat by reducing the threshold of heat receptor (TRPV1) activation from 109 °F (43 °C) to 85 °F (29 °C).[12] The pain may be caused by the overproduction of a protein called CXCL5, which activates nerve fibers.[13]

Skin type determines the ease of sunburn. People with lighter skin tones and limited capacity to develop a tan after UV radiation exposure have a greater risk of sunburn. Fitzpatrick's Skin phototypes classification describes the normal variations of skin responses to UV radiation. Persons with type I skin have the greatest capacity to sunburn, and type VI have the least capacity to burn. However, all skin types can develop sunburn.[14]

Fitzpatrick's skin phototypes:

Age also affects how skin reacts to the sun. Children younger than six and adults older than sixty are more sensitive to sunlight.[16]

Certain genetic conditions, for example, xeroderma pigmentosum, increase a person's susceptibility to sunburn and subsequent skin cancers. These conditions involve defects in DNA repair mechanisms which decrease the ability to repair DNA damaged by UV radiation.[17]

Medications

The risk of sunburn can be increased by

tranquillizers have this effect.[18]

UV intensity

The

UV Index indicates the risk of sunburn at a given time and location. Contributing factors include:[16]

  1. The time of day. In most locations, the sun's rays are strongest between approximately 10 am and 4 pm daylight saving time.[19]
  2. Cloud cover. Clouds partially block UV, but even on an overcast day, a significant percentage of the sun's damaging UV radiation can pass through clouds.[20][21]
  3. Proximity to reflective surfaces, such as water, sand, concrete, snow, and ice. All of these reflect the sun's rays and can cause sunburns.
  4. The season of the year. The Sun's position in late spring and early summer can cause a more-severe sunburn.
  5. Altitude. At a higher altitude, it is easier to become burnt, because there is less of the Earth's atmosphere to block the sunlight. UV exposure increases about 4% for every 1000 ft (305 m) gain in elevation.
  6. Proximity to the equator (latitude). Between the polar and tropical regions, the closer to the equator, the more direct sunlight passes through the atmosphere over a year. For example, the southern United States gets fifty percent more sunlight than the northern United States.
Erythemal dose rate at three Northern latitudes. (Divide by 25 to obtain the UV Index.) Source: NOAA.

Because of variations in the intensity of UV radiation passing through the atmosphere, the risk of sunburn increases with proximity to the

solar noon when shadows are at their minimum, and the Sun's radiation passes most directly through the atmosphere. Regardless of one's latitude (assuming no other variables), equal shadow lengths mean equal amounts of UV radiation.[citation needed
]

The skin and eyes are most sensitive to damage by UV at 265–275 nm wavelength, which is in the lower UVC band that is rarely encountered except from artificial sources like welding arcs. Longer wavelengths of UV radiation cause most sunburn because those wavelengths are more prevalent in ground-level sunlight.[citation needed]

Ozone depletion

In recent decades, the incidence and severity of sunburn have increased worldwide, partly because of chemical damage to the atmosphere's ozone layer. Between the 1970s and the 2000s, average stratospheric ozone decreased by approximately 4%, contributing an approximate 4% increase to the average UV intensity at the Earth's surface. Ozone depletion and the seasonal "ozone hole" have led to much larger changes in some locations, especially in the southern hemisphere.[22]

Tanning

sun protection factor (SPF) of 3, meaning that tanned skin would tolerate up to three times the UV exposure as pale skin.[24]

Sunburns associated with indoor tanning can be severe.[25]

The World Health Organization, American Academy of Dermatology, and the Skin Cancer Foundation have recommended avoiding artificial UV sources such as tanning beds. Suntans are not recommended as a form of sun protection.[26][27][28]

Diagnosis

A sunburned leg below the shorts line

Differential diagnosis

The differential diagnosis of sunburn includes other skin pathology induced by UV radiation, including photoallergic reactions, phototoxic reactions to topical or systemic medications, and other dermatologic disorders that are aggravated by exposure to sunlight. Considerations for diagnosis include duration and intensity of UV exposure, topical or systemic medication use, history of dermatologic disease, and nutritional status.

Additionally, since sunburn is a type of

radioactivity. Excess radiation exposure may result in acute radiation syndrome or other radiation-induced illnesses, especially in sunny conditions. For instance, the difference between the erythema caused by sunburn and other radiation burns is not immediately obvious. Symptoms common to heat illness and the prodromic stage of acute radiation syndrome like nausea, vomiting, fever, weakness/fatigue, dizziness or seizure can add to further diagnostic confusion.[32]

Prevention

UV Index
) is the product of the sunlight spectrum at the Earth's surface (radiation intensity) and the erythemal action spectrum (skin sensitivity). Long-wavelength UV is more prevalent, but each milliwatt at 295 nm produces almost 100 times more sunburn than at 315 nm.
Skin peeling on the upper arm as a result of sunburn – the destruction of lower layers of the epidermis causes rapid loss of the top layers
Tanning
of the forearm (visible darkening of the skin) after extended sun exposure

The most effective way to prevent sunburn is to reduce the amount of UV radiation reaching the skin. The World Health Organization, American Academy of Dermatology, and Skin Cancer Foundation recommend the following measures to prevent excessive UV exposure and skin cancer:[33][34][35]

  • Limiting sun exposure between the hours of 10 am and 4 pm, when UV rays are the strongest
  • Seeking shade when UV rays are most intense
  • Wearing sun-protective clothing, including a wide-brim hat, sunglasses, and tightly woven, loose-fitting clothing
  • Using sunscreen
  • Avoiding tanning beds and artificial UV exposure

UV intensity

The strength of sunlight is published in many locations as a

UV Index. 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 pm, but often one to two hours later. Seeking shade using umbrellas and canopies can reduce UV exposure, but does not block all UV rays. The WHO recommends following the shadow rule: "Watch your shadow – Short shadow, seek shade!"[33]

Sunscreen

Commercial preparations that block UV light are known as

sun 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. The stated protection factors are correct only if 2 mg of sunscreen is applied per square cm of exposed skin translates into about 28 mL (1 oz) to cover the whole body of an adult male. The recommended dose is much more than many people use in practice.[36] Sunscreens function as chemicals such as oxybenzone and dioxybenzone (organic sunscreens) or opaque materials such as zinc oxide or titanium oxide (inorganic sunscreens) that mainly absorb UV radiation. Chemical and mineral sunscreens vary in the wavelengths of UV radiation blocked. Broad-spectrum sunscreens contain filters that protect against UVA radiation as well as UVB. Although UVA radiation does not primarily cause sunburn, it contributes to skin aging and increases skin cancer risk.[citation needed
]

Sunscreen is effective and thus recommended for preventing

basal cell carcinoma.[39] Typical use of sunscreen does not usually result in vitamin D deficiency, but extensive usage may.[40]

Recommendations

Research has shown that the best sunscreen 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 after activities such as swimming, sweating, and rubbing.[41] Recommendations are product dependent varying from 80 minutes in water to hours based on the indications and protection shown on the label. The American Academy of Dermatology recommends the following criteria in selecting a sunscreen:[42]

  • Broad spectrum: protects against both UVA and UVB rays
  • SPF 30 or higher
  • Water resistant: sunscreens are classified as water resistant based on time, either 40 minutes, 80 minutes, or not water resistant

Eyes

The eyes are also sensitive to sun exposure at about the same UV wavelengths as skin;

freckles
, are often found within the iris.

The tender skin of the eyelids can also become sunburned and can be especially irritating.[citation needed]

Lips

The

lips can become chapped (cheilitis) by sun exposure. Sunscreen on the lips does not have a pleasant taste and might be removed by saliva. Some lip balms (ChapSticks) have SPF ratings and contain sunscreens.[citation needed
]

Feet

The skin of the feet is often tender and protected, so sudden prolonged exposure to UV radiation can be particularly painful and damaging to the top of the foot. Protective measures include sunscreen, socks, or swimwear that covers the foot.

Diet

Dietary factors influence susceptibility to sunburn, recovery from sunburn, and risk of secondary complications. Several dietary

antioxidants, including essential vitamins, are effective in protecting against sunburn and skin damage associated with ultraviolet radiation, in both human and animal studies. Supplementation with Vitamin C and Vitamin E was shown in one study to reduce the amount of sunburn after a controlled amount of UV exposure.[46]
A review of scientific literature through 2007 found that
beta carotene (Vitamin A) supplementation had a protective effect against sunburn. The effects of beta carotene were only evident in the long-term, with studies of supplementation for periods less than ten weeks in duration failing to show any effects.[47] There is also evidence that common foods may have some protective ability against sunburn if taken for a period before exposure.[48][49]

Protecting children

Babies and children are particularly susceptible to UV damage which increases their risk of both melanoma and non-melanoma skin cancers later in life. Children should not sunburn at any age, and protective measures can reduce their future risk of skin cancer.[50]

  • Infants 0–6 months: Children under 6mo generally have skin too sensitive for sunscreen and protective measures should focus on avoiding excessive UV exposure by using window mesh covers, wide-brim hats, loose clothing that covers the skin, and reducing UV exposure between the hours of 10am and 4pm.
  • Infants 6–12 months: Sunscreen can safely be used on infants this age. It is recommended to apply a broad-spectrum, water-resistant SPF 30+ sunscreen to exposed areas and avoid excessive UV exposure by using wide-brim hats and protective clothing.
  • Toddlers and Preschool-aged children: Apply a broad-spectrum, water-resistant SPF 30+ sunscreen to exposed areas, use wide-brim hats and sunglasses, avoid peak UV intensity hours of 10 am - 4 pm and seek shade. Sun-protective clothing with an SPF rating can also provide additional protection.

Artificial UV exposure

The WHO recommends that artificial UV exposure, including tanning beds, should be avoided as no safe dose has been established.[51] Special protective clothing (for example, welding helmets/shields) should be worn when exposed to any artificial source of occupational UV. Such sources can produce UVC, an extremely carcinogenic wavelength of UV, which ordinarily is not present in normal sunlight, having been filtered out by the atmosphere.[citation needed]

Treatment

The primary measure of treatment is avoiding further exposure to the sun. The best treatment for most sunburns is time; most sunburns heal completely within a few weeks.

The American Academy of Dermatology recommends the following for the treatment of sunburn:[52]

anesthetics such as benzocaine, however, are contraindicated.[55] Schwellnus et al. state that topical steroids (such as hydrocortisone cream) do not help with sunburns,[54] although the American Academy of Dermatology says they can be used on especially sore areas.[55] While lidocaine cream (a local anesthetic) is often used as a sunburn treatment, there is little evidence for the effectiveness of such use.[56]

A home treatment that may help the discomfort is using cool and wet cloths on the sunburned areas.

soy.[55] Furthermore, sunburn draws fluid to the skin's surface and away from the rest of the body. Drinking extra water is recommended to help prevent dehydration.[55]

See also

References

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  2. ^ a b World Health Organization, International Agency for Research on Cancer "Solar and ultraviolet radiation" Archived 29 July 2013 at the Wayback Machine IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 55, November 1997
  3. ^ a b Sunburn at eMedicine
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External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Sunburn&oldid=1214663528"