Unlike UV-A, all UV-C and approximately 90% of UV-B is filtered by the ozone layer, so no UV-C and only 10% of UV-B reaches the earth. Exposure to UV-C may result from welding arcs, bactericidal lamps, and mercury arc lamps. UVR's depth of skin penetration depends upon the wavelength, with longer wavelengths having deeper penetration. Approximately 90% of UV-B is absorbed by the epidermis, while 50% of UV-A reaches the basal layer or deeper.

Since the 1920s, a tanned appearance has been a symbol of health and wealth, often indicating the ability to travel to sunny areas. Outdoor recreational activities have increased sun exposure and thus the risk of sunburn. In 1996, 79% of Canadians reported an average of at least 30 minutes daily exposure to the summer sun; 32% reported 1-2 hours, and 28% reported 2 or more hours. A 1996 US survey of adults older than 18 years showed that 83% had at least 1 hour of weekday exposure during the summer, and 93% had more than 1 hour of weekend exposure; most of this exposure occurred between 10 am and 4 pm.

A tan is the skin's response to injury produced by UVR; there is no such thing as a "safe" tan.

Children receive approximately 3 times more sun exposure than adults. Approximately 50-80% of an individual's estimated lifetime sun exposure occurs during childhood and adolescence.

In quest of a tan, use of artificial tanning beds and sun lamps has become common, particularly by women, but artificial tanning devices are associated with the same risks as exposure to UVR from sunlight. Over the past 10 years, the idea that a tan is healthy has gradually lost favor because sun exposure has become strongly associated with skin cancer, immunosuppression, cataract formation, and photoaging. Blistering sunburns, particularly during childhood, significantly increase an individual's subsequent risk of developing cutaneous melanoma.

Ozone layer thickness varies with the seasons. The layer above North America is thickest in late winter, thinnest in late summer and early fall. The ozone layer has been decreasing. Reactive nitrogen compounds (eg, nitrous oxide, nitrogen dioxide), halogens (eg, chlorine, bromine), and hydrogen compounds can destroy the ozone layer. Nitrogen gases (from supersonic aircraft, air pollution, fertilizers, and microorganisms), chlorofluorocarbons (CFCs) (used as refrigerants and in aerosols, extruded foam, and solvents), and bromine-containing halons (in fire extinguishers) contribute to ozone layer depletion.

Buildup of greenhouse gas (eg, carbon dioxide) traps heat near the earth's surface, cools the stratosphere, and increases ozone loss. A 1% decrease in ozone results in a 1-2% increase in UV-B and a consequent 2% increase in skin cancers. Clouds and air pollution have little effect on UVR, since as much as 80% of UVR penetrates. UVR also penetrates 1-meter depths of water.

UVR exposure increases 4% for each 300-meter rise in altitude. Reflection from sand, pavement, snow, and water also increases UVR exposure. Humidity increases susceptibility to sunburn. The equator receives the greatest amount of UVR throughout the year.

UV index

The UV index was introduced in 1994 to forecast UVR intensity. UV index ratings and associated risks, based upon the estimated extent of exposure required to cause sunburn in a fair-skinned person, are as follows:

• Zero to 2 - Minimal risk (1-hr exposure required to sunburn)
• Three to 4 - Low risk (20-min exposure required to sunburn)
• Five to 6 - Moderate risk (<15-min exposure required to sunburn)
• Seven to 9 - High risk (<10-min exposure required to sunburn)
• Ten or more - Extreme risk (<5-min exposure required to sunburn)

History: Patients with sunburn have a history of excessive sun exposure from outdoor recreation or work, and, less frequently, a history of concomitant ingestion of PO medications or application of topical agents.

• All individuals develop sunburns from large doses of UVR, although persons with darker skin burn less frequently.

• Persons with blue or green eye color, lighter skin, and those who tan poorly and freckle easily are more prone to sunburn.

• If the patient has received the threshold dose of UVR, delayed skin erythema in exposed areas occurs in 2-6 hours, peaks at 15-36 hours, and resolves within 72-120 hours.

• Individuals with fair skin (eg, SPT 1 and 2) may have a history of immediate transient flush.

• The trunk, neck, and head burn at lower UVR doses than upper limbs; upper limbs burn more readily than lower limbs.

• According to the 1996 Canadian National Survey, the area most commonly sunburned was the back and shoulders, followed by the arms and legs, then face, scalp and neck, and chest.

• Erythema following UV-A exposure from sun beds begins immediately, peaks at approximately 8 hours, and persists 24-48 hours.

Physical:

• Confluent erythema and warmth are present in exposed areas.

• Edema, pain and tenderness, and pruritus may occur as a result of moderate-to-severe sun exposure.

• Vesiculation occurs in severe cases of sunburn and may require a week or longer to resolve.

• Complications due to secondary infection are infrequent.

• Scaling or peeling occurs a few days following exposure.

• Nausea, abdominal cramping, weakness and malaise, fever, chills, and headache also may occur, most often with severe sunburn.

• Patients with severe sunburn may have a rapid pulse rate.

Causes: Although exposure to UV-B light causes most sunburns, use of tanning salons and home tanning devices have made UV-A–induced sunburn increasingly common.

• Severe sunburns often result after falling asleep at the beach or under a UV lamp or from prolonged exposure at swimming areas.
• Both outdoor work and outdoor recreational activities are risk factors for sunburn.
• Sunburn is common when residents of northern latitudes have prolonged sun exposure while vacationing in southern latitudes or near the equator.
• Outdoor exposure on cloudy days may give people a false sense of protection. As much as 80% of UVR penetrates clouds.
• Reflective surfaces such as sand, snow, water, and cement may contribute to sunburn development.
• Increased humidity reduces the threshold for erythema caused by UVR.
• Medical treatments that expose patients to UV-B and UV-A may cause a sunburn reaction.
• UV-C exposure from welding arcs, bactericidal lamps, and mercury arc lamps may cause sunburn.
• The degree of sunburn depends upon duration and intensity of exposure, patient’s skin type or complexion, and previous conditioning of the skin.
• The unit of measurement of a sunburn is the MED, defined as the minimum UV-B exposure required to produce a clearly marginated erythema in an irradiated site following a single exposure. MED is expressed as mJ/cm².
• Phototoxic reactions resulting in a sunburn reaction usually occur in the UV-A range and can be caused by topical and systemic agents. In contrast to photoallergic reactions, phototoxic reactions may occur after the initial exposure and do not affect areas of the body that were protected from light.

• Topical agents causing phototoxic reactions

• Bergamot oil (5-methoxypsoralen)
• Coal tar derivatives
  • Acridine
  • Anthracene
  • Fluoranthene
  • Naphthalene
  • Phenanthrene
  • Pyridine
  • Thiopene
• Dyes/pigments
  • Acriflavine
  • Anthraquinone
  • Cadmium sulfate
  • Eosin
  • Methylene blue
  • Rose bengal
  • Toluidine blue

• Methoxsalen
• Plants (furocoumarins)
  • Leguminoseae family
  • Moraceae family - Figs
  • Rutaceae family - Bergamot orange, gas plant, lemon, lime
  • Umbellifereae family - Angelica, anise, bishop weed, celery, cow parsley, dill, fennel, giant hogweed, wild parsnip, wild carrot

• Retinoids (after continued use)
  • Adapalene
  • Tazarotene
  • Vitamin A acid
• Tar

• Systemic agents causing phototoxic reactions

• Antimicrobials
  • Ceftazidime
  • Griseofulvin
  • Quinolones - Ciprofloxacin, nalidixic acid, norfloxacin, ofloxacin
  • Sulfonamides
  • Tetracyclines - Doxycycline, tetracycline
  • Trimethoprim

• Antineoplastic agents
  • Dacarbazine
  • 5-fluorouracil
  • Vinblastine
• Antimalarials - Quinine
• Cardiac medications
  • Amiodarone
  • Quiidine
• Diuretics
  • Furosemide
  • Hydrochlorothiazide

• Hematoporphyrin
• Hypolipidemics - Clofibrate
• Nonsteroidal anti-inflammatory agents (NSAIDs)
  • Diclofenac
  • Ibuprofen
  • Indomethacin
  • Ketoprofen
  • Naproxen
  • Piroxicam
  • Sulindac
  • Tiaprofenic acid

• Psoralens
  • Methoxsalen
  • Trioxalen
• Antipsychotics
  • Alprazolam
  • Chlordiazepoxide
  • Chlorpromazine
  • Desipramine
  • Imipramine
  • Perphenazine
  • Prochlorperazine
  • Thioridazine
  • Trifluoperazine

• Retinoids
  • Acitretin
  • Isotretinoin
• Sulfonylureas - Tolbutamide
• Sulfites

Lab Studies:
 

• Except for patients with severe sunburn, laboratory studies rarely are indicated and usually are ordered only if the diagnosis is unclear.

• Manage cases of severe sunburn as burn cases; order appropriate laboratory studies and monitor for fluid and electrolyte imbalance and for risk of secondary infection.

Imaging Studies:
 

• No imaging studies are required for patients with sunburn.

Other Tests:
 

• If porphyria is suspected, order blood, urine, and stool porphyrins.

• If systemic lupus erythematosus (SLE) is suspected, order antinuclear antibody (ANA) serology, anti-Ro, and anti-La antibody titers.

• Phototesting may show an abnormally low erythemal threshold in chronic actinic dermatitis and may induce the disorder.

• Patch testing and photopatch testing may identify a contact or photocontact allergen.

• If secondary infection is suspected, order microbiology tests.

Procedures:

• Skin biopsy usually is unnecessary because diagnosis usually is easy to confirm from the history and clinical findings.

Histologic Findings: Histology rarely is required because diagnosis usually is confirmed clinically, although it may help distinguish sunburn from photosensitivity disorders. Histologic changes may occur before clinical signs or symptoms appear, sometimes as early as 30 minutes after exposure.

Medical Care: A sunburn is considered a self-limited injury. Even a mild sunburn requiring no treatment, however, provides an excellent opportunity to teach patients about the risks of sun exposure and use of photoprotection.

Patients with moderate sunburn should be encouraged to replenish their fluids with nonalcoholic beverages. Those with mild-to-moderate sunburn may require relief of pain or pruritus.

Severe sunburn requires admission to a burn unit for parenteral fluid replacement, pain control, and prophylaxis against infection.

Patients presenting with a vesicular reaction should not have the vesicles unroofed, since the epidermal surface of the blister provides protection against secondary infection.

After a sunburn, the skin should not be exposed to the sun for at least a week because the skin is more susceptible to burning. Nonpharmacologic treatment for sunburn includes the following:

• Direct the patient to stay in a shaded cool environment for a few days, with bed rest as necessary.

• Cool baths or cool tap water (depending on the affected surface area) or saline solution compresses for 20 minutes, repeated 3-4 times daily may offer some relief from pain and pruritus.

• Applying calamine or pramoxine lotion 3 times daily to affected areas may help.

• Moisturizers, applied liberally and frequently, help reduce dryness and peeling in mild sunburns.

• Bath preparations (eg, colloidal oatmeal) are helpful, but direct patients to use soaps sparingly.

• Ointments or butter do not help a mild-to-moderate sunburn and may be painful to wash off.

Surgical Care: Blistering sunburns may require treatment within a hospital burn unit.

Consultations: Refer patients who have experienced a bad sunburn or who have burned while on a photosensitizing medication to a dermatologist. Other possible consultations include the following:

• Plastic surgery

• Ophthalmology (if corneal injury suspected)

Diet: N/A

Topical vitamin E, if applied within 2 minutes of excessive UV exposure, may reduce erythema and edema. However, because clinical effects of sunburn do not appear for some time after exposure, the risk of sunburn may not be appreciated at the time of exposure.

Oral indomethacin or ibuprofen, or topical indomethacin 1%, administered immediately after sun exposure may reduce erythema and degree of epidermal insult.

Decrease erythema by applying glycolic acid 12% topically qid starting 4 h after UV-B exposure and glycolic acid 8% daily starting 24 h after UV-B exposure. Three weeks of pretreatment with 8% glycolic acid cream 8% results in an SPF of approximately 2.4.

Some emergency departments and burn units continue to administer systemic corticosteroids, although the effectiveness of these drugs has not been established. Systemic corticosteroid administration has little beneficial effect in sunburn treatment and may increase the risk of secondary infection.

Potent topical corticosteroids transiently reduce erythema, but do not influence epidermal damage. Topical corticosteroids may provide some relief of stinging or itching when applied bid/tid and provide an additive effect to indomethacin or ibuprofen. Avoid prolonged administration of potent steroids.

Acetaminophen or aspirin may offer some relief of associated pain, although opioid analgesics may be necessary in severe situations.

Diphenhydramine (Benadryl) or hydroxyzine HCL (Atarax) 25-75 mg hs may help patients sleep and relieve itching, but provide no other sunburn management benefits.

Discourage use of topical diphenhydramine and topical anesthetic sprays because of allergic contact dermatitis risk.
 

Drug Category: Anti-inflammatory agents -- Help reduce erythema and degree of epidermal insult.

Drug Category: Analgesics -- May offer some pain relief, although opioid analgesics may be necessary in severe situations.

Drug Category: Dermatologic agents -- Used to decrease erythema.

Drug Category: Antihistamines -- May help patient sleep and provide relief from itching, but provide no additional benefit in management of sunburn.

Further Inpatient Care:

• N/A

Further Outpatient Care:

• Patients with mild-to-moderate sunburn do not require close monitoring.

• Closely follow patients with extensive burns and dehydration to assess their needs for fluid replacement and treatment of infection.

• Caution patients and parents to watch for signs of secondary infection in cases of severe sunburn. Instruct patients and parents to seek medical care for drainage, foul smell, or increasing redness or fevers associated with disruption of the natural skin barrier.

In/Out Patient Meds:

• N/A

Transfer:

• N/A

Deterrence/Prevention:

• The association between repeated sun exposure and sunburns with the development of skin cancer and premature aging highlights the importance of preventive practices.
• Early intervention and education during childhood maximize the effects of preventive practices. Encourage adults to teach sun protection to their children. Infants and small children may be unable to avoid sun exposure on their own.
• Encourage patients who desire a tanned appearance to try self-tanning gels or lotions (eg, dihydroxyacetone), which do not increase the risk of skin cancer or wrinkling. (These gels and lotions offer no sun protection.)
• Sunburn prevention may involve behavioral and pharmacological components. The following behaviors minimize the risk of sunburn:

• Avoid prolonged exposure during the middle of the day (ie, 10 am-4 pm), particularly during summer months.
• Avoid prolonged sun exposure when the UV index is high.
• Sit or play in the shade whenever possible. Umbrellas may decrease UVR by approximately 70% but offer little protection against reflected radiation. Shade from trees (unless in a dense forest), awnings, and buildings, while helpful, provide insufficient UVR protection (ie, SPF typically <4).
• Wear appropriate protective clothing and accessories (eg, long pants, long-sleeved shirts, hats, and sunglasses).
  • Patients who have excessive exposure to sunlight or who have histories of skin cancer should consider buying clothing specifically designed to protect from UVR.
  • Dark, dry, tightly woven clothing offers the most protection. When fabric is wet, water occupies the spaces between the fibers and allows greater UVR penetration. Women’s stockings provide minimal protection. Synthetic fabrics (eg, rayon) offer greater protection than cotton clothing.
  • Recently developed commercial products (eg, Rit Sun Guard with Tinosorb) add UV protection to clothing. The product is added to the clothes washing cycle, and a single treatment reportedly remains effective through 20 washings.
  • Wear hats with wide brims (eg, >7.5 cm) of tightly woven material (not straw) to protect the face, ears, and neck. Baseball caps, depending upon how they are worn, often inadequately protect the ears, nose, and back of the neck.

• Avoid cosmetic tanning and tanning salons.
• Avoid or minimize sun exposure while taking phototoxic medications or topical agents that may interact with UV/visible light to cause a dose-related sunburn.

• Pharmacologic aspects of sunburn prevention include chemical and physical sunscreens. No sunscreen offers 100% photoprotection, so consider sunscreen only as an adjunctive photoprotective measure.
• No truly effective PO sunscreens exist. Antimalarial drugs, vitamin A or E, betacarotene, and PO p-aminobenzoic acid (PABA) do not provide adequate sun protection. Combined systemic vitamin C at 2 g/d and vitamin E at 1000 IU/d provide minimal protection (SPF 1.4); topical application in a sunscreen may enhance sun protection.
• Sunscreens are meant to protect the skin and not to prolong sun exposure. Although sunscreens can prevent sunburn, UVR-induced immunosuppression and carcinogenicity may occur before the UV erythema threshold is reached. Daily sunscreen use for 4.5 years has been associated with a decline in the incidence of squamous cell carcinoma.

   

• Sunscreen selection

• Seek out a sunscreen with an SPF number of 30 or more (ie, "high protection"), preferably a product that offers protection against both UV-B and UV-A. (SPFs ranging from 1-11 are rated "minimal protection" and SPFs ranging from 12-29 are rated "moderate protection.")
• If sunscreens with high SPF ratings are unavailable, use sunscreens with an SPF of at least 15. Sunscreens rated at SPF 15 block approximately 93% of UV-B radiation, compared to the 97% block provided by SPF 30.

• Sunscreen use

• Apply sunscreen 15-60 minutes prior to UV exposure to allow proper skin binding.
• Generously apply topical sunscreens to all exposed surfaces, including often forgotten areas such as the lips, ears, neck, and dorsum of feet; approximately 30 mL is required to cover the body completely.
• Reapply sunscreens after swimming, toweling, or sweating because these activities remove some of the sunscreen. Waterproof sunscreens are more substantive (ie, maintain efficacy after 80-min water immersion) than water-resistant sunscreens (ie, maintain efficacy after 40-min water immersion); either is more effective than sweat-resistant sunscreens (ie, maintain efficacy after 30-min continuous heavy sweating).
• Reapplication does not extend the period of protection.

• Physical sunscreens reflect and scatter UV and are useful for all ages. Examples include titanium dioxide, zinc oxide, talc, kaolin, ferric chloride, and melanin. Titanium dioxide and zinc oxide also absorb UVR and, therefore, are considered both chemical and physical sunscreens.
  • Physical sunscreens tend to be thicker, less cosmetically appealing, and more easily rubbed off, although micronized titanium dioxide and zinc oxide are relatively transparent and more cosmetically pleasing.
  • Although physical sunscreens offer reduced risk of sensitization, their occlusive effect may cause miliaria and folliculitis.

• UV-B absorbers
  • Benzylidene camphor derivative (4-methylbenzylidene camphor) - Photostabilizer for dibenzoylmethanes
  • Cinnamates - Easily removed with swimming and sweating; may cross react with balsam of Peru, benzyl and methyl cinnamate, cinnamic alcohol, cinnamic aldehyde, cinnamon, cinnamon oil, cocoa leaves
    • 2-ethoxyethyl p-methoxycinnamate (Cinoxate)
    • Octocrylene
    • Octyl methoxycinnamate (Parsol MCX)
  • PABA esters (eg, octyl dimethyl PABA [Padimate O]) - May induce contact/photocontact dermatitis; may cross-react with ester anesthetics, sulfonamides, sulfonylurea hypoglycemics, thiazides
  • Salicylates - Easily removed with swimming or sweating; rare cause of contact dermatitis
    • Octyl salicylate
    • Homomenthyl salicylate (homosalate)
    • Triethanolamine salicylate

• UV-A absorbers
  • Anthranilates (methyl anthranilate) - Incomplete UV-A protection (max absorption: 332-345 nm); rare cause of contact dermatitis
  • Benzophenones - Broad-spectrum with UV-A II/UV-B protection
    • Dioxybenzone (benzophenone-8) - may induce contact dermatitis and contact urticaria
    • Oxybenzone (benzophenone-3) - may induce contact and photocontact dermatitis
  • Dibenzoylmethanes (eg, t-butylmethoxy-dibenzoylmethane, avobenzone, Parsol 1789) - Broad UV-A II and I protection; photodegradable; may induce contact and photocontact sensitization

Complications:

• Closely monitor patients with extensive burns and dehydration to assess their need for fluid replacement and their risk of secondary infection.

• Sunburned skin rarely leads to scarring after healing unless secondary infection occurs.

Prognosis:

• Prognosis for most sunburns is excellent.

• The long-term effects of sunburn increase the patient's risk for skin cancer, lentigines, and photoaging.

Patient Education:

• Teach patients about the harmful effects of the sun and how to provide appropriate sun protection for the entire family. Patients should be taught that there is no such thing as a “healthy” tan, and that sunburns are more easily prevented than treated.

• Direct patients to avoid or minimize sun exposure during the peak times of sunburning (ie, 10 am-4 pm) when the UV index is high. (A memorable reminder for patients is to tell them the peak times are "whenever your shadow is shorter than you.")

• Instruct patients to avoid sunbathing.

• Encourage parents to use sun protection themselves as well as to provide it for their children. Research has found that parents who used sun protection themselves were more likely to provide sun protection for their child, compared to parents who do not use sun protection for themselves.

• Encourage susceptible persons (eg, those with SPTs 1 or 2 and/or those with outdoor occupations) to apply sunscreen every day along with their daily cosmetic regimen.

• Remind young patients who enjoy tanning about the unattractive dyspigmentation and wrinkling associated with chronic sun exposure, not to mention the increased future risk of developing cutaneous malignancy.

• Make patients aware of the UV index, which indicates the sunlight intensity based on weather conditions. Many weather forecasts now feature this information.

• Encourage patients to perform regular skin self-examinations and to seek periodic professional examinations from their physicians.