SUNBURN

The solar radiation that strikes the earth includes 50% visible light (wavelength 400 to 760 nanometers [nm]), 40% infrared (760 to 1,700 nm), and 10% ultraviolet (UV) (10 to 400 nm) (Figure 119). Energetic rays (e.g., cosmic rays, gamma rays, and x-rays) with wavelengths shorter than 10 nm do not penetrate to the earth’s surface to any significant degree. Sunburn is a cutaneous photosensitivity reaction caused by exposure of the skin to ultraviolet radiation (UVR) from the sun. There are four types of UVR: vacuum UVR is 10 to 200 nm (absorbed by air and unable to penetrate Earth’s atmosphere), UVA is 320 to 400 nm, UVB is 290 to 320 nm, and UVC is 100 to 290 nm. UVC is filtered out by the ozone layer of the atmosphere. UVB is the culprit in the creation of sunburn and cancer. UVA is of less immediate danger but is a serious cause of skin aging, drug-related photosensitivity, and skin cancer. Furthermore, persons taking immunosuppressive agents for medical reasons (e.g., acquired immunodeficiency syndrome [AIDS] or cancer) may be more predisposed to skin cancer caused by UVA.

Figure 119 Solar radiation.

Ultraviolet exposure varies with the time of day (greatest between 9 a.m. and 3 p.m. because of increased solar proximity and decreased angle of light rays), season (greater in summer), altitude (8% to 10% increase per each 1,000 ft, or 305 m, of elevation above sea level), location (greater near the equator), and weather (greater in the wind). Snow or ice reflects 85% of UVR, dry sand 17%, and grass 2.5%. Water may reflect 10% to 100% of UVR, depending on the time of day, location, and surface. However, UVR at midday may penetrate up to 24 in (60 cm) through water. Clouds absorb 10% to 80% of UVR, but rarely more than 40%. Most clothes reflect (light-colored) or absorb (dark-colored) UVR. A dry white cotton shirt has a maximum sun protection factor (SPF) of 8 (see Sunscreens, below). However, it is important to note that wet cotton of any color probably transmits considerable UVR.

Skin darkening occurs immediately on UVA exposure, as preformed melanin is released, and lasts for 15 to 30 minutes. Tanning occurs after 3 days of exposure, as additional melanin is produced. If the skin is not conditioned with gradual doses of UVR (tanning), a burn can be created. A person’s sensitivity to UVR depends on his skin type and thickness, the pigment (melanin) in his skin, and weather conditions. Well-hydrated skin is penetrated four times as effectively by UVR as is dry skin, because the moist skin does not scatter or reflect UVR as well.

Depending on the exposure, the injury can range from mild redness to blistering and disablement. Rapid pigment darkening from immediate melanin release is followed by the redness with which we are all familiar, caused by dilation of superficial blood vessels. This begins 2 to 8 hours after exposure and reaches its maximum (the “burn”) in 24 to 36 hours, with associated itching and pain.

Wind appears to augment the injury, as do heat, atmospheric moisture, and immersion in water. “Windburn” is not possible without UVR or abrasive sand. Since windburn is due in part to the drying effect of low humidity at high altitudes, it can be helpful to protect the skin with a greasy sunscreen or barrier cream.

People may be more sensitive to UVR after they have ingested certain drugs (such as tetracycline, doxycycline, fluoroquinolones, vitamin A derivatives, nonsteroidal antiinflammatories, sulfa derivatives, minoxidil, diltiazem, nifedipine, thiazide diuretics, hypoglycemic agents, chloroquine, dapsone, quinidine, carbamazepine, chemotherapeutic drugs, and barbiturates) or have been exposed to certain plants (such as lime, citron, bitter orange, lemon, celery, parsnip, fennel, dill, wild carrot, fig, buttercup, mustard, milfoil, agrimony, rue, hogweed, Queen Anne’s lace, and stinking mayweed). Your eyes may become more sensitive to light (e.g., you may need to wear sunglasses at a lower UV threshold) if you are taking certain medications, such as digoxin, quinidine, tolazamide, or tolbutamide.

For a mild sunburn in which no blistering is present, the victim may be treated with cool liquid compresses, cool showers, a nonsensitizing skin moisturizer (such as Vaseline Intensive Care), and aspirin or a nonsteroidal antiinflammatory drug, such as ibuprofen, to decrease the pain and inflammation. Topical anesthetic sprays, many of which contain benzocaine and/or diphenhydramine, should in general be avoided, because they can cause sensitization and an allergic reaction. Menthol-containing lotions may be helpful. Topical steroids do not appreciably diminish a sunburn.

If the victim is deep red (“lobster”) without blisters, a stronger antiinflammatory drug, such as prednisone, may be given. A 5-day course of prednisone (80 mg on the first day, 60 mg the second, 40 mg the third, 20 mg the fourth, and 10 mg the fifth) may decrease the discomfort of “sun poisoning,” which is the constellation of low-grade fever, loss of appetite, nausea, and weakness that accompanies a bad total-body sunburn. Corticosteroids should always be taken with the understanding that a rare side effect is serious deterioration of the head (“ball” of the ball-and-socket joint) of the femur, the long bone of the thigh. An extensive nonblistering first-degree sunburn can make the victim nauseated and weak, with low-grade fever and chills. He should be forced to drink enough balanced electrolyte-supplemented liquids to avoid dehydration (see page 208).

Topical steroid creams, such as pramoxine with hydrocortisone (Pramosone cream or lotion) may be used if blisters are not present. Pramoxine alone (Prax) is a nonsensitizing topical anesthetic. Topical steroid preparations should not be applied to blistered skin, because wound healing may be delayed and infection made likelier. On the other hand, aloe vera lotion or gel may be soothing and promote healing. Vitamin E is an antioxidant that, when mixed with aloe vera, may soothe the skin. However, this hasn’t been proven to promote healing any better than aloe vera alone. Other remedies that have been suggested include bathing in a tub of water augmented by baking soda or oatmeal, or applying 0.1% diclofenac gel.

With a severe sunburn in which blistering is present, the victim has by definition suffered second-degree burns (see page 108) and should be treated accordingly. Gently clean the burned areas and cover with sterile dressings. Administer appropriate pain medication.

SUNSCREENS

Sunscreens (available as lotions or creams) either absorb light of a particular wavelength, act as barriers, or reflect light. There is no evidence that any ingredients in sunscreens cause skin damage or cancer. Choose sunscreens based on your estimated exposure and on your own propensity to tan or burn. There is no such thing as a “safe tan,” even when sunscreens are used, because sun exposure is directly linked to skin cancer. In addition, long-term exposure to UVR from sunlight causes premature skin aging and loss of skin tone. The term photoaging refers to these effects—increased wrinkles, loose skin, brown spots, a leathery appearance, and uneven pigmentation.

Dermatologists classify sun-reactive skin types (based on the first 45 to 60 minutes of sun exposure after winter or after a prolonged period of no sun exposure) as follows:

In all cases it is wise to overestimate the protection necessary and to carry a strong sunscreen. To protect hair from sun damage, wear a hat.

Para-aminobenzoic acid (PABA) derivatives, which are water soluble, are sunscreens that absorb UVB (not UVA) and that accumulate in the skin with repeated application. The most commonly used PABA derivative is padimate O (octyl dimethyl PABA). The most effective method of application is to moisturize the skin (shower or bathe) and then apply the sunscreen. For maximum effect, chemical sunscreens should be applied liberally (most people only apply ¼ to ½ of what they need) at least 15 to 30 minutes before exposure, and the skin should be kept dry for at least 2 hours after sunscreen application. Sun blockers, such as titanium, are effective essentially immediately. When PABA itself is used, a recommended preparation is 5% to 10% PABA in 50% to 70% alcohol. However, PABA is now used infrequently because its absorption peak of UVB at 296 nm is too far from 307 nm, where UVB exerts its greatest effect. Furthermore, it causes skin irritation—a stinging sensation—and can stain cotton and synthetic fabrics. PABA derivatives are less problematic.

Benzophenones are sunscreens that are more effective against UVA. These should be used in 6% to 10% concentration. Because they are not well absorbed by the skin, they require frequent reapplication. Photoplex broad-spectrum sunscreen lotion contains a PABA-ester combined with a potent UVA absorber, Parsol 1789. This is an excellent sunscreen for sensitive people, particularly those at risk for drug-induced photosensitivity. The Food and Drug Administration (FDA) has approved Anthelios SX (L—Oreal), which has SPF (see below) 15 and contains three active ingredients, one of which is ecamsule (a stable UVA sunscreen), which has been marketed as Meroxyl SX in Europe and Canada since 1993. Sunscreens come in different concentrations (such as PreSun “8” or “15”). A higher sun protection factor (SPF) number (range 2 to 50) indicates a greater degree of protection against UVB. “Minimal erythema dose” (MED) is the amount of UVR exposure required to redden the skin. SPF is derived by dividing the MED of skin covered with sunscreen by the MED of unprotected skin. Thus, an SPF of 15 indicates that it requires 15 times the UVR exposure to achieve a sunburn as it would without protection. The SPF number assumes a liberal (approximately 1¼ oz, or 37 mL, per adult) application of the sunscreen. In general, a sunscreen with an SPF number of 8 or less will allow tanning, probably by ultraviolet A exposure. There is no standard for measuring UVA protection. Persons with sensitive or unconditioned skin should use a sunscreen with an SPF number of 10 or greater. Fair-skinned people who never tan or who tan poorly (Types I, II, or III) or mountain climbers (there is more UV exposure at higher altitudes, and more is reflected off snow) should always use a sunscreen with an SPF number of 15 or greater. Most sun exposure occurs before age 18 years, so it is very important to apply sunscreens to children and young adults.

Substantivity refers to the ability of a sunscreen to resist water wash-off. Layering sunscreens doesn’t work well, because the last layer applied usually washes off. Current specialty sunscreens with high substantivity include Bullfrog Water Pro Body Gel, Aloe Gator Total Sun Block Lotion, and Dermatone Ultimate Fisherman’s Sunscreen.

Sunscreens are first applied to cool, dry skin for optimal absorption; wait 10 minutes before water exposure. Reapply them liberally after swimming or heavy perspiration. In general, most sunscreens should be reapplied every 20 minutes to 2 hours. Be aware that the concomitant use of insect repellent containing DEET (see page 390) lowers the effectiveness of the sunscreen by a factor of one-third. Although many sunscreens are designed to bond or adhere to the skin under adverse environmental conditions, there are certain situations in which any sunscreen should be reapplied at a maximum of 3- to 4-hour intervals:

Some authorities recommend using sunscreens of at least SPF 29, with the rationale that most people underapply or improperly apply them. Bald-headed men should protect their domes. All children should be adequately protected. However, avoid PABA-containing products in children less than 6 months old. Those sensitive to PABA can use Piz-Buin, Ti-Screen, Sawyer Products Stay-Put Sun Block, Uval, and Solbar products. Eating PABA does not protect the skin.

For total protection against ultraviolet and visible light, a preparation can be composed from various mixtures of titanium dioxide, red petrolatum, talc, zinc oxide, kaolin, red ferric oxide (calamine), and ichthammol. These preparations or similar commercial products (“glacier cream”) are used for lip and nose protection. Micronized titanium dioxide and zinc oxide can be prepared in an invisible preparation (such as Ti-Screen Natural 16 and Neutrogena Chemical Free 17) that does not cause skin irritation. Sunscreens that prevent infrared transmission may help prevent flares of fever blisters caused by herpes virus. An improvised sunscreen can be prepared by preparing a sludge of ashes from charcoal or wood, or from ground clay. In a pinch, axle grease will work to some degree.

If you are concerned about jellyfish stings, a useful product is Safe Sea Sunblock with Jellyfish Sting Protective Lotion (www.buysafesea.com), which is both a sunscreen and a jellyfish sting inhibitor.

Substances that are ineffective as sunscreens and that may increase the propensity to burn include baby oil, cocoa butter, and mineral oil. Promising antioxidant substances under investigation as effective sunscreens are vitamins A, C, and E, and chemicals found in green tea.

Although “tanning tablets” or “bronzers” induce a pigmentary change in the skin that resembles a suntan, they provide minimal, if any, true protection from the effects of ultraviolet exposure. Like the sun, indoor tanning machines induce skin changes that lead to premature skin aging and cancer. The best tan derived from the natural sun’s UVB carries an SPF of approximately 2; a tanning bed supplies UVA and therefore no protection.

Taking aspirin or a nonsteroidal antiinflammatory drug (such as ibuprofen) at 6-hour intervals three times before sun exposure may help protect the sun-sensitive person.

Many effective sunscreens, particularly those advertised to stay on in the water, are extremely irritating to the eyes, so take care when applying these to the forehead and nose. Near the eyes, avoid sunscreens with an alcohol or propylene glycol base. Instead, use a sunscreen cream.

There are also sunscreen/insect repellent combinations, such as Coppertone Bug & Sun. Avon Bug Guard contains Skin-So-Soft (mostly mineral oil) in combination with picaridin or IR3535, and in at least one version, it is enhanced by a sunscreen.

A line of medical clothing, Solumbra by Sun Precautions, is advertised to be “soft, lightweight and comfortable,” and offers 30-plus SPF protection. Solar Protective Factory also manufactures high-SPF protective clothing. Women’s hosiery has an unacceptably low SPF. The ability of Lycra to block UVR varies depending on whether it is lax (very effective) to stretched (nearly ineffective). Dry, white cotton (T-shirt) has an SPF of 5 to 8. The ultraviolet protection factor (UPF) is a measure of UVR protection provided by a fabric. Thus, a UPF of 15 indicates that 1/15 of the UVR that strikes the surface of the fabric penetrates through to the skin. A chemical UVR protectant, Tinosorb FD (Rit Sun Guard), may be used as a laundry additive, increasing the UPF of washed clothing up to 50.

UVR protection provided by hats depends on the style. Broad-brimmed hats and “bucket” hats provide the most protection for the face and head. Sunday Afternoons manufactures comfortable broad-brimmed hats with neck shields advertised to provide 97% UV block. Legionnaires hats do a decent job of protection, but baseball caps leave many facial areas exposed. If you are wearing a helmet, add a visor.

MELANOMA

Melanoma is a type of skin cancer that can be caused by ultraviolet B light exposure. Indeed, regular use of a sunscreen with an SPF of at least 15 during the first 18 years of life may reduce the lifetime risk of developing melanoma by more than 75%. People with white skin and a tendency to burn rather than tan are at increased risk for the development of melanoma.

Although you wouldn’t self-treat a melanoma, it is important for those who spend a great deal of time outdoors to recognize the features of skin cancer. Regularly inspect existing moles, birthmarks, and other skin lesions. Since melanoma is often found on a person’s back or other area that cannot be easily inspected, it is important to have a knowledgeable person (such as a dermatologist) inspect all suspicious skin lesions from time to time.

Warning signs within a skin lesion include the following:

If you note any of these features, see a dermatologist for a proper evaluation. Basal cell carcinoma and squamous cell carcinoma are two other types of cancer associated with UVR exposure.

POISON IVY, SUMAC, AND OAK (GENUS TOXICODENDRON)

The rashes of poison ivy, poison sumac, and poison oak are caused by a resin (urushiol) found in the resin canals of leaves, stems, vines, berries, and roots (Figure 120). The resin is not found on the surface of the leaves. The potency of the sap does not vary with the seasons. In its natural state, the oil is colorless; on exposure to air, oxidation causes it to turn black. Because the plant parts have to be injured to leak the resin, most cases are reported in spring, when the leaves are most fragile. Dried leaves are less toxic, because the oil has returned to the stem and roots through the resin canals. However, smoke from burning plants carries the residual available resin in small particles and can cause a severe reaction on the skin and in the nose, mouth, throat, and lungs.

Figure 120 A, Poison oak. B, Poison ivy. C, Poison sumac.

The poison oak group does not grow in Alaska or Hawaii, and it rarely grows above 4000 ft (1219 m). Other plants or parts of plants that contain urushiol include the India ink tree, mango rind, cashew nut shell, and Japanese lacquer tree. A smaller number of reactions are caused by the poisonwood tree found in the southern tip of Florida. Because the resin is long lived, it can be spread by contact with tents, clothing, and pet fur.

Sensitivity to the resin varies with each individual, and can present for the first time at any age. The first exposure produces a rash in 6 to 25 days. Subsequent exposures can cause a rash in 8 hours to 10 days, with a 2- to 3-day interval most common. Unless the resin is removed from the skin within 10 minutes of exposure, a reaction is inevitable in sensitive individuals. It is generally accepted that the resin binds to the skin within 30 minutes, is completely bound to the skin within 8 hours, and is likely impossible to remove effectively with soap and water after just 60 minutes. Some highly sensitive persons will suffer a reaction even if the resin is washed off within 1 minute of exposure.

The rash begins with itching followed by redness, followed by lines of reddened bumps and blisters. The skin may swell, blisters grow, and weeping/oozing lesions develop. Swelling of the tissues can be quite severe. After approximately a week, the rash begins to dry, and scabs begin to form, particularly if the victim has done much scratching and rubbing. This is followed by thickening and darkening of the skin, which may last for many weeks.

After exposure, it is usually most convenient to remove the resin with soap and cool water, but to be most effective, washing must occur within 30 minutes. Rubbing alcohol is a better solvent for the resin than is water. Zanfel Poison Ivy Wash (Zanfel Laboratories) is a soap mixture of ethoxylate and sodium lauroyl sarcosinate surfactants that binds to urushiol on the skin so that it can be washed off. The instructions for use (to treat an area the size of an adult hand or face) are to wet the affected area; squeeze a minimum 1½ inch ribbon of Zanfel into one palm and then wet and rub both hands together for 10 seconds to work the product into a paste; rub both hands on the affected area for up to 3 minutes to work the Zanfel into the skin until there is no itching; and rinse the area thoroughly. If the itch returns, repeat the process. Tecnu Outdoor Skin Cleanser (alkane and alcohol) (Tec Labs) works quite well when applied soon after exposure, rubbed in for 2 minutes, and rinsed off, with a repeat of the entire sequence. Tecnu Extreme Medicated Poison Ivy Scrub is advertised to be effective after a 15-second application. Another wash designed to remove urushiol is Dr. West’s Ivy Detox Cleanser, which contains magnesium sulfate. Herbal remedies that have been claimed (but never proven) to be effective are jewelweed (Impatiens capensis), which is an ingredient in Burt’s Bees Poison Ivy Soap, witch hazel bark, and aloe plant.

For treatment of the skin reaction, shake lotions such as calamine are soothing and drying, and they control itching. A good nonsensitizing topical anesthetic is pramoxine hydrochloride 1% (Prax cream or lotion); Caladryl contains calamine and pramoxine. Avoid topical diphenhydramine, benzocaine, and tetracaine. Antihistamines (such as diphenhydramine [Benadryl]) control itching and act as sedatives. Nonsedating antihistamines, such as fexofenadine (Allegra), may also diminish itching. A soothing bath in tepid (not hot) water with half a 1 lb box of baking soda, 2 cups (551 ml) of linnet starch, or 1 cup (275 mL) Aveeno oatmeal is excellent. If Aveeno is not available, a woman’s nylon stuffed with regular (not instant) oatmeal can be thrown in the tub. Soothing aluminum acetate in water (1:20) soaks may help, as might aluminum subacetate (Burow’s solution, Domeboro), which comes as a 5% solution that should be diluted to a 1:40 concentration. When these soaks are used, they should be applied as cotton-soaked wet dressings 3 to 4 times a day for 15 to 30 minutes per application to dry out the weeping rash. Topical steroid creams are generally of little value. Potent topical steroid ointments are not effective unless they are applied before the appearance of blisters and continued for 2 to 3 weeks, so are not recommended. Alcohol applications are painful and do not hasten resolution of the rash. There are new topical agents, such as pimecrolimus (Elidel) 1% cream and tacrolimus (Protopic) 0.03% or 0.1% ointment, which modulate the immune system and are effective without causing skin atrophy, as would be caused by a superpotent topical steroid.

If the reaction is severe (facial or genital involvement or intolerable itching), the victim should be treated with a course of oral prednisone (80 to 100 mg each of the first 3 days, then decreased by 10 mg every 2 days until the final dose is 10 mg—80, 80, 70, 70, 60, 60, and so on). Corticosteroids should always be taken with the understanding that a rare side effect is serious deterioration of the head (“ball” of the ball-and-socket joint) of the femur, the long bone of the thigh. At the end of the course of corticosteroids, the victim may suffer a “flare-up” of the rash and symptoms, which may be treated with a repeated course of medication.

Once the resin has been removed from the skin, the rash and blister fluid are not contagious. However, if the resin is still present, touching the involved skin will allow resin to be transferred to other areas. All clothes, sleeping bags, and pets should be washed with soap and water, because the resin can persist for years, particularly on woolen garments and blankets.

For prevention, there are few commercially available topical chemical preparations that act as effective barriers, although it appears that activated charcoal, aluminum oxide, and silica gel may work. Multi Shield (Interpro) is a protective agent for sensitive individuals. It should be applied over any sunscreen, and must be washed off carefully after use according to instructions. Stokogard Outdoor Cream is a linoleic acid dimer barrier cream preparation that is advertised to provide up to 8 hours of skin protection. Hollister Moisture Barrier and Hydropel may prove useful as barriers. IvyBlock (Enviroderm Pharmaceuticals) contains bentoquatam, which acts as a barrier. It is applied at least 15 minutes before going outdoors and then every 4 hours. Antiperspirants are used anecdotally as barriers, but have not been proven effective.

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