Sunburn
Prevention Use of sunscreen, sun protective clothing
Sunburn is a form of
radiation burn that affects living tissue, such as skin, that results from an
overexposure to ultraviolet (UV) radiation, usually from the Sun. Common
symptoms in humans and other animals include: red or reddish skin that is hot
to the touch or painful, general fatigue, and mild dizziness. Other symptoms
include blistering, peeling skin, swelling, itching, and nausea. Excessive UV
radiation is the leading cause of (primarily) non-malignant skin tumors, and in
extreme cases can be life-threatening. Sunburn is an inflammatory response in
the tissue triggered by 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.
Sun protective measures
including sunscreen and sun protective clothing are widely accepted to prevent
sunburn and some types of skin cancer. Special populations, including children,
are especially susceptible to sunburn and protective measures should be used to
prevent damage.
Typically, there is initial
redness, followed by varying degrees of pain, proportional in severity to both
the duration and intensity of exposure.
Other symptoms can include
blistering, swelling (edema), itching (pruritus), peeling skin, rash, nausea,
fever, chills, and fainting (syncope). Also, a small amount of heat is given
off from the burn, caused by the concentration of blood in the healing process,
giving a warm feeling to the affected area. Sunburns may be classified as
superficial, or partial thickness burns. Blistering is a sign of second degree
sunburn.
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.
Duration
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 strongest 6 to 48 hours after exposure. The burn continues to develop
for 1 to 3 days, occasionally followed by peeling skin in 3 to 8 days. Some
peeling and itching may continue for several weeks.
Skin cancer
Ultraviolet radiation causes
sunburns and increases the risk of three types of skin cancer: melanoma,
basal-cell carcinoma and squamous-cell carcinoma. Of greatest concern is that
the melanoma risk increases in a dose-dependent manner with the number of a person's
lifetime cumulative episodes of sunburn. It has been estimated that over 1/3 of
melanomas in the United States and Australia could be prevented with regular
sunscreen use.
Causes
The cause of sunburn is the
direct damage that a UVB photon can induce in DNA (left). One of the possible
reactions from the excited state is the formation of a thymine-thymine
cyclobutane dimer (right).
Sunburn is caused by UV
radiation from the sun, but "sunburn" may result from artificial
sources, such as tanning lamps, welding arcs, or ultraviolet germicidal
irradiation. It is a reaction of the body to direct DNA damage from UVB light.
This damage is mainly the formation of a 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.
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
and the generation of free radicals, thus indirect DNA damage. 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. These
sensitive sites often occur at biologically significant locations near genes.
Sunburn causes an
inflammation process, including 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). The pain may be caused by overproduction of
a protein called CXCL5, which activates nerve fibres.
Skin type determines the
ease of sunburn. In general, people with lighter skin tone and limited capacity
to develop a tan after UV radiation exposure have a greater risk of sunburn.
The 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.
Fitzpatrick's skin
phototypes:
Type 0: Albino
Type I: Pale white skin,
burns easily, does not tan
Type II: White skin, burns
easily, tans with difficulty
Type III: White skin, may
burn but tans easily
Type IV: Light brown/olive
skin, hardly burns, tans easily
Type V: Brown skin, usually
does not burn, tans easily
Type VI: Black skin, very
unlikely to burn, becomes darker with UV radiation exposure.
Age also affects how skin
reacts to sun. Children younger than six and adults older than sixty are more
sensitive to sunlight.
There are certain genetic
conditions, for example xeroderma pigmentosum, that increase a person's
susceptibility to sunburn and subsequent skin cancers. These conditions involve
defects in DNA repair mechanisms which in turn decreases the ability to repair
DNA that has been damaged by UV radiation.
Medications
The risk of a sunburn can be
increased by pharmaceutical products that sensitize users to UV radiation.
Certain antibiotics, oral contraceptives, antidepressants, acne medications,
and tranquillizers have this effect.
UV intensity
The UV Index indicates the
risk of getting a sunburn at a given time and location. Contributing factors
include
The time of day. In most
locations, the sun's rays are strongest between approximately 10am and 4pm
daylight saving time.
Cloud cover. UV is partially
blocked by clouds; but even on an overcast day, a significant percentage of the
sun's damaging UV radiation can pass through clouds.
Proximity to reflective
surfaces, such as water, sand, concrete, snow, and ice. All of these reflect
the sun's rays and can cause sunburns.
The season of the year. The
position of the sun in late spring and early summer can cause a more-severe
sunburn.
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.
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 the course of 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 tropic latitudes, located between 23.5° north
and south latitude. All else being equal (e.g., cloud cover, ozone layer,
terrain, etc.), over the course of a full year, each location within the tropic
or polar regions receives approximately the same amount of UV radiation. In the
temperate zones between 23.5° and 66.5°, UV radiation varies substantially by
latitude and season. The higher the latitude, the lower the intensity of the UV
rays. Intensity in the northern hemisphere is greatest during the months of
May, June and July — and in the southern hemisphere, November, December and
January. On a minute-by-minute basis, the amount of UV radiation is dependent
on the angle of the sun. This is easily determined by the height ratio of any
object to the size of its shadow (if the height is measured vertical to the
earth's gravitational field, the projected shadow is ideally measured on a
flat, level surface; furthermore, for objects wider than skulls or poles, the
height and length are best measured relative to the same occluding edge). The
greatest risk is at 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.
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 almost never encountered except from artificial sources like
welding arcs. Most sunburn is caused by longer wavelengths, simply because
those are more prevalent in sunlight at ground level.
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.
Tanning
Suntans, which naturally
develop in some individuals as a protective mechanism against the sun, are
viewed by most in the Western world as desirable. This has led to an overall
increase in exposure to UV radiation from both the natural sun and tanning
lamps. Suntans can provide a modest sun protection factor (SPF) of 3, meaning
that tanned skin would tolerate up to three times the UV exposure as pale skin.
Sunburns associated with
indoor tanning can be severe.
The World Health
Organization, American Academy of Dermatology, and the Skin Cancer Foundation
recommend avoiding artificial UV sources such as tanning beds, and do not
recommend suntans as a form of sun protection.
Diagnosis
Skin showing sunburn 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, use of topical or systemic medications, history of dermatologic
disease, and nutritional status.
Phototoxic reactions: This
refers to a non-immunological response to sunlight interacting with certain
drugs and chemicals in the skin which resembles an exaggerated sunburn. Common
drugs that may cause a phototoxic reaction include amiodarone, dacarbazine,
fluoroquinolones, 5-fluorouracil, furosemide, nalidixic acid, phenothiazines,
psoralens, retinoids, sulfonamides, sulfonylureas, tetracyclines, thiazides,
and vinblastine.[26]
Photoallergic reactions: This
refers to an uncommon immunological response to sunlight interacting with
certain drugs and chemicals in the skin. When in excited state by UVR, these
drugs and chemicals form free radicals that react to form functional antigens
and induce a Type IV hypersensitivity reaction. These drugs include
6-methylcoumarin, aminobenzoic acid and esters, chlorpromazine, promethazine,
diclofenac, sulfonamides, and sulfonylureas. Unlike phototoxic reactions which
resemble exaggerated sunburns, photoallergic reactions can cause intense
itching and can lead to thickening of the skin.
Phytophotodermatitis: UV
radiation induces inflammation of the skin after contact with certain plants
(including limes, celery, and meadow grass). Causes pain, redness, and
blistering of the skin in the distribution of plant exposure.
Polymorphic light eruption: This
is a recurrent abnormal reaction to UVR. It can present in various ways
including pink-to-red bumps, blisters, plaques and urticaria.
Solar urticaria: UVR-induced
wheals that occurs within minutes of exposure and fades within hours.
Other skin diseases
exacerbated by sunlight: Several dermatologic conditions can increase in
severity with exposure to UVR. These include systemic lupus erythematosus
(SLE), dermatomyositis, acne, atopic dermatitis, and rosacea.
Additionally, since sunburn
is a type of radiation burn, it can initially hide a severe exposure to
radioactivity resulting in acute radiation syndrome or other radiation-induced
illnesses, especially if the exposure occurred under 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.
Prevention
Sunburn effect (as measured
by the 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 arm as a
result of sunburn – the destruction of lower layers of the epidermis causes
rapid loss of the top laye
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:
Limiting sun exposure
between the hours of 10am and 4pm, 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 noon, but often one to two
hours later. Seeking shade including using umbrellas and canopies can reduce
the amount of UV exposure, but does not block all UV rays. The WHO recommends
following the shadow rule: "Watch your shadow – Short shadow, seek
shade!"
Commercial preparations are
available that block UV light, known as sunscreens or sunblocks. They have a
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. 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.[33] Sunscreens function as chemicals such as oxybenzone and
dioxybenzone that absorb UV radiation (chemical sunscreens) or opaque materials
such as zinc oxide or titanium oxide to physically block UV radiation (physical
sunscreens).[34] 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 does contribute to skin aging and an increased risk of skin
cancer.
Sunscreen is effective and
thus recommended for preventing melanoma[ and squamous cell carcinoma.[36]
There is little evidence that it is effective in preventing basal cell
carcinoma. Typical use of sunscreen does
not usually result in vitamin D deficiency, but extensive usage may.
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 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. The
American Academy of Dermatology recommends the following criteria in selecting
a sunscreen.
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; snow blindness is
essentially sunburn of the cornea. Wrap-around sunglasses or the use by
spectacle-wearers of glasses that block UV light reduce the harmful radiation.
UV light has been implicated in the development of age-related macular
degeneration, pterygium and cataract. Concentrated clusters of melanin, commonly
known as freckles, are often found within the iris.
The tender skin of the
eyelids can also become sunburned and can be especially irritating.
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.
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, and swimwear or swimgear that covers the foot.
Diet
Dietary factors influence
susceptibility to sunburn, recovery from sunburn, and risk of secondary
complications from sunburn. Several dietary antioxidants, including essential
vitamins, have been shown to have some effectiveness for 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. A review of scientific literature through 2007 found that beta
carotene (Vitamin A) supplementation had a protective effect against sunburn,
but that the effects were only evident in the long-term, with studies of
supplementation for periods less than 10 weeks in duration failing to show any
effects. There is also evidence that common foods may have some protective ability
against sunburn if taken for a period before the exposure.
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 ensure their future risk of skin cancer
is reduced.
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 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 as well as
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
10am-4pm and seek shade. Sun protective clothing with a 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. When one is
exposed to any artificial source of occupational UV, special protective
clothing (for example, welding helmets/shields) should be worn. 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.
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:
For pain relief, take cool
baths or showers frequently.
Use soothing moisturizers
that contain aloe vera or soy.
Anti-inflammatory
medications such as ibuprofen or aspirin can help with pain.
Keep hydrated and drink
extra water.
Do not pop blisters on a
sunburn; let them heal on their own instead.
Protect sunburned skin (see:
Sun Protective Clothing and Sunscreen) with loose clothing when going outside
to prevent further damage while not irritating the sunburn.
Non-steroidal
anti-inflammatory drugs (NSAIDs; such as ibuprofen or naproxen), and aspirin
may decrease redness and pain. Local anesthetics such as benzocaine, however,
are contraindicated Schwellnus et al.
state that topical steroids (such as hydrocortisone cream) do not help with
sunburns, although the American Academy of Dermatology
says they can be used on especially sore areas. While lidocaine cream (a local
anesthetic) is often used as a sunburn treatment, there is little evidence for
the effectiveness of such use.
A home treatment that may help the discomfort
is using cool and wet cloths on the sunburned areas. Applying soothing lotions that contain aloe
vera to the sunburn areas was supported by multiple studies, though others have found aloe vera to have no
effect. Note that aloe vera has no ability to protect people from new or
further sunburn.
Jan Ricks Jennings, MHA,
LFACHE
Senior Executive
Senior Management
Resources, LLC
Jan.Jennings@EagleTalons.net
JanJenningsBlog.Blogspot.com
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724.733.0509 Office
February 20, 2022
