Skin disorders

Sunburn

The solar radiation that strikes the earth includes 50% visible light (wavelength 400 to 760 nanometers [nm]), 40% infrared (760 to 1700 nm), and 10% ultraviolet (10 to 400 nm) ( Fig. 163 ). 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. While UVA is of less immediate danger in relation to sunburn, it is a serious cause of skin aging, drug-related photosensitivity, and skin cancer. Furthermore, persons taking immunosuppressive agents for medical reasons (e.g., AIDS or cancer) might be more predisposed to skin cancer caused by UVA.

Ultraviolet exposure varies with the time of day (greatest between 9 am and 3 pm because of increased solar proximity and decreased angle of light rays), season (greater in summer), altitude (8% to 10% increase per each 1000 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 can reflect 10% to 100% of UVR, depending on the time of day, location, and surface. However, UVR at midday can penetrate up to 24 inches (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 their skin type (e.g., Fitzpatrick Skin Type, ranging from 1 to 6, with 1 being white skin-high sunburn susceptibility-poor tanning and 6 being very dark skin-very low sunburn susceptibility-very good tanning) and thickness, the pigment (melanin) in their 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 caused by dilation of superficial blood vessels. This begins 2 to 6 hours after exposure and reaches its maximum (the “burn”) in 12 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 might be more sensitive to UVR and more readily suffer sunburn or develop skin rashes after they have ingested certain drugs (such as tetracycline, doxycycline, fluoroquinolones, vitamin A derivatives, nonsteroidal antiinflammatory drugs [NSAIDs], 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 might become more sensitive to light (e.g., you might 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 an NSAID, to decrease the pain and inflammation. Topical diclofenac gel 0.1% might help relieve pain and redness. Pramoxine alone (Prax) is a nonsensitizing topical anesthetic. Because sunburn might cause itching, topical remedies that might be effective include nonsensitizing pramoxine lotion, pramoxine plus camphor plus calamine (Aveeno anti-itch) lotion, and lidocaine plus camphor (Neutrogena Norwegian Formula moisturizer). Sarna lotion contains pramoxine and sometimes contains menthol. Menthol shaving cream may be used to moisturize and soften the skin. Anecdotal remedies for mild sunburn include application for 5 to 10 minutes of Greek yogurt, or application of aloe, baking soda, or bathing in a tub of water augmented by baking soda or oatmeal (Aveeno). Vitamin E is an antioxidant that, when mixed with aloe vera, might soothe the skin. However, this has not been proved to promote healing any better than aloe vera alone, which itself is not an evidence-based recommendation. Topical steroids (e.g., triamcinolone 0.1% cream applied bid when erythema first appears) may blanch reddened skin but should not be used on blistered skin. Pramoxine with hydrocortisone (Pramosone cream or lotion) may be used.

If the victim is deep red (“cooked 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) can decrease the discomfort of “sun poisoning,” which is the constellation of low-grade fever, chills, loss of appetite, nausea, and weakness that accompanies an extensive nonblistering total-body first degree sunburn. They should be forced to drink enough balanced electrolyte-supplemented liquids to avoid dehydration (see page 230).

With a severe sunburn in which blistering is present, the victim has by definition suffered second-degree burns (see page 128) and should be treated accordingly. Gently clean the burned areas and cover with sterile dressings. Do not use corticosteroids. Administer appropriate pain medication.

Sunscreens

Sunscreens prevent sunburn and skin cancer. There is no evidence that any ingredients in sunscreens cause skin damage or cancer. However, recent evaluations indicate that under manufacturers’ maximal recommended use (reapply every 2 hours), certain sunscreen active components (avobenzone, oxybenzone, octocrylene, homosalate, octisalate, octinoxate, and ecamsule) can be measured in the blood at a level (0.5 ng/mL) that warrants safety assessment per the U.S. Food and Drug Administration (FDA). There is not yet any change in user directions to indicate that people should refrain from using certain sunscreens, but this might be modified as more safety data are accumulated. The consensus is that the safest sunscreens are zinc oxide and titanium dioxide.

Sunscreens are available as lotions and creams (spread easily and penetrate well); gels (nongreasy but wash or sweat off easily); waxes and ointments (preferable for extreme conditions and resist chapping); oils (spread easily but might cause blackheads); and sprays (wasteful and might form an uneven layer). They either absorb light of a particular wavelength, act as barriers, or reflect light. “Broad-spectrum sunscreens” protect against both UVA and UVB rays. 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:

• Type I: Always burns easily, never tans. Fair-skinned people with a high number of moles are at the greatest risk for melanoma.

• Type II: Always burns easily, tans minimally.

• Type III: Burns moderately, tans gradually and uniformly (light brown).

• Type IV: Burns minimally, always tans well (moderate brown).

• Type V: Rarely burns, tans profusely (dark brown).

• Type VI: Never burns, is deeply pigmented (black skin).

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.

Sunscreens come in different concentrations (such as PreSun “8” or “15”). A higher SPF number indicates a greater degree of protection against UVB. SPF ranges from 2 (absorbs 50% of UVB) to 100 (absorbs 99% of 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 1 ¼ oz, or 37 mL, per adult) application of the sunscreen. Because sunscreens are rarely perfectly applied, it is best to assume a markedly lower (approximately 50%) SPF than stated on the label. In general, a sunscreen with an SPF number of 8 or less will allow tanning, probably by UVA exposure. There is no standard for measuring UVA protection. Persons with sensitive or unconditioned skin should use a sunscreen with an SPF number of 50 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 50 or greater. Most sun exposure occurs before 18 years of age, 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 does not 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. Water resistance claims on sunscreen labels must indicate whether the sunscreen remains effective for 40 minutes or 80 minutes while swimming or sweating.

The most effective method of application is to moisturize the skin (shower or bathe) and then apply the sunscreen to cool, dry skin. 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 sun exposure, and the skin should optimally be kept dry for at least 2 hours after sunscreen application. If you are going to enter the water, apply sunscreen at least 15 to 30 minutes before entry. Sun blockers, such as titanium, are effective essentially immediately.

In general, most sunscreens should be reapplied every 20 minutes to 2 hours, depending on the environmental conditions and wash off. Be aware that the concomitant use of insect repellent containing DEET (see page 381) 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:

• Continuous sun exposure, particularly between the hours of 10 am and 3 pm

• Exposure at altitude of 7000 ft (2135 m) or higher

• Exposure within 20 degrees latitude of the Equator

• Exposure during May through July in the Northern Hemisphere, and December through February in the Southern Hemisphere

• Frequent water immersion, particularly with toweling off

• Preexisting sunburn or skin irritation

• Ingestion of drugs, such as certain antibiotics, that can cause photosensitization

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). 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 (e.g., avobenzone) 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 or plant-induced (e.g., lime juice on the skin) photosensitivity. Other effective UVA blockers include ecamsule and micronized titanium dioxide or zinc oxide. An excellent sunscreen is Sawyer STAY PUT sunscreen, which comes in a variety of SPF ratings.

Some authorities recommend using sunscreens of at least SPF 50, 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. Persons 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. In this regard, Blue Lizard Australian Sensitive Sunscreen SPF 30+ is an excellent product. Sunscreens that prevent infrared transmission might help prevent flares of fever blisters caused by herpes virus. An improvised sunscreen can be made 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 jellyfish sting inhibitor.

Substances that are ineffective as sunscreens and that might 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. Furthermore, tanning beds do not stimulate enough natural production of vitamin D to be worth the risk of developing skin cancer. There is no such thing as a safe tan.

Taking aspirin or an NSAID at 6-hour intervals three times before sun exposure might 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.

Take care to cover the lips with a strong sunscreen or lip balm, such as Extreme Weather Lip Balm.

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.

Sun protection from clothing is determined by the nature of the material, tightness of weave (better when not stretched out), color (dark is better), and moisture (dry is better). A line of medical clothing, Solumbra by Sun Precautions, is advertised to be “soft, lightweight and comfortable,” and offers 100+ 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), can 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 block 97% of UV. 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.

To summarize the most important ways to have sunscreens be effective:

• Apply sunscreens liberally and cover all exposed areas. Sunscreens are tested at 2 milligrams per square centimeter of skin to determine their SPF. That does not directly translate into volume. Use at least ½ teaspoon for each of the head and neck, and arm; 1 teaspoon per leg; 2 to 3 tablespoons to cover your chest and back; and if you are bald or have thinning hair, do not forget the top of your head. Reapply every couple of hours, especially in dry conditions. Use a sunscreen with SPF of at least 50, and do not be afraid to use one of higher SPF.

• Apply sunscreens at least 15 to 30 minutes in advance of exposure.

• Reapply sunscreens after swimming, bathing, sweating, or otherwise washing them off the skin.

• Insect repellent applied at the same time as a sunscreen reduces effectiveness of the sunscreen.

• Anticipate intense UVR exposure at high altitude, on the water, and even on cloudy days.

Photolyase is an enzyme harvested from plankton extract that is reported to lessen damage to the DNA of cells that is caused by UVR exposure. There is evolving science indicating that this might become an important ingredient in topical lotions or creams applied after UVR exposure has occurred. There are “DNA repair” products on the market (promoted for anti-aging) that might one day be recommended to minimize or prevent cell damage and the inflammatory response that are part of sunburn.

Sunscreens that have been banned in Hawaii because they cause damage to coral reefs include the chemicals oxybenzone, octocrylene, and octinoxate. Another reef ecology consideration is to avoid “nanomineral” preparations of zinc or titanium. Inactive sunscreen ingredients that damage coral reefs include parabens, microbeads, and formaldehyde-releasing components. Read the back label to determine what is in the sunscreen.

Sunglasses for eye protection against UVR are discussed on page 210.

Melanoma

Melanoma is a type of skin cancer that can be caused by ultraviolet light exposure (particularly sunburn), with UVB more causative than UVA. Indeed, regular use of a sunscreen with an SPF of at least 15 during the first 18 years of life might 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 developing melanoma. Tanning bed use is thought to be associated with increased risk for melanoma, particularly in young women.

Although you would not self-treat a melanoma, it is important for those who spend a great deal of time outdoors to recognize the features of skin cancer, which also includes basal cell and squamous cell cancers. 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 (particularly a mole) include the following “ABCDE”:

• A—Asymmetry: (one portion different from the rest, with respect to shape, color, darkness, or texture).

• B—Border: that is irregular, ragged, jagged, notched, or blurred. The color might spread into surrounding skin.

• C—Color: that is uneven. Variation in color within the lesion or discoloration (black, dark brown, tan, blue, red, white, mottled)

• D—Diameter: changing; usually growing. Melanomas are usually greater in diameter than a pencil eraser but can sometimes be smaller.

• E—Evolving: change in appearance or features (size, color, texture, sensation, bleeding, itching, tenderness, scaling). If a mole looks different than others on the body, it is suspicious.

If you notice any of these features, see a dermatologist for a proper evaluation.

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 ( Fig. 164 ). 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 must 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.

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 nutshell, 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. Poison ivy and oak have three-leaf clusters, not five to seven leaves. Woody vines with 5 leaves include the Virginia creeper and woodbine.

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 2 to 3 days 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 might 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 might 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 benzocaine, and tetracaine. Avoid topical diphenhydramine in children under the age of 2 years. Antihistamines (such as diphenhydramine [Benadryl]) control itching and act as sedatives. Nonsedating antihistamines, such as fexofenadine (Allegra) or loratadine (Claritin), can also diminish itching. A soothing bath in tepid (not hot) water with half of 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. Aluminum acetate in water (1:20) soaks can be soothing, 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 three to four 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 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 super potent 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). At the end of the course of corticosteroids, the victim might suffer a “flare-up” of the rash and symptoms, which can 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 might 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 might 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.

Other irritating plants

Poodle-dog bush (Eriodictyon parryi) is a purple-flowered plant that when touched can cause a reaction ranging from mild skin irritation with or without blistering to breathing difficulty. It is treated like a poison oak exposure.

Some plants produce thorns/spines/spicules, fluids, or crystals that act as primary irritants to the skin, in a nonallergic reaction, causing combinations of burning sensation, itching, and swelling. These plants include buttercup, croton bush, spurge, manchineel, beach apple, daisy, mustard, radish, pineapple, lemon, crown of thorns, milkbush, candelabra cactus, daffodil, hyacinth, stinging nettle, itchweed, dogwood, barley, millet, prickly pear, snow-on-the-mountain, primrose, geranium, meadow rue, narcissus, oleander, opuntia cactus, mesquite, tulip, mistletoe, wolfsbane, and horse nettle.

The skin should be thoroughly washed with soap and water. If barbs are embedded in the skin, removal might be easiest if you apply the sticky side of adhesive tape to the skin, and then peel the barbs off embedded to the tape.

Small cactus spines or the spicules of a stinging nettle can be removed by applying the sticky side of adhesive (duct) tape and peeling it off, or spreading a facial gel (mask or peel) or rubber cement, allowing it to dry, and peeling it off. Large spines can be removed with forceps. This might be necessary if the barbs on the cactus spine inhibit easy removal with the adhesive-tape method. A single cactus thorn can be as sharp as a needle and penetrate easily through the skin without leaving an external mark.

Medicated soaks recommended by dermatologists for plant-induced skin irritation include aluminum acetate solution (1:20) or Dalibour (Dalidane) solution (copper and zinc sulfate and camphor). Administration of corticosteroids (such as prednisone) is not useful for a primary (nonallergic) skin irritation.

Giant hogweed creates sap that when touched makes skin become sensitive to light, with burns and blisters. If it gets into the eyes, it is painful and can cause visual loss. Cow parsnip causes a similar, but lesser, reaction.

Rashes incurred in the water

Hives

Hives (urticaria) are one skin manifestation of an allergic reaction or might develop as part of a nonallergic reaction (such as to a medication). Hives appear as raised, red, and irregularly bordered welts or thickened patches of skin ( Fig. 165 ). Often, the victim will also complain of itching and/or fever. The treatment for hives presumed to be caused by allergy is to administer an antihistamine (such as diphenhydramine, cetirizine, or levocetirizine) at prescribed intervals until the rash has begun to subside and the itching is relieved, and to observe the victim closely for progression to a serious allergic reaction. Hives can appear in moments yet take days to completely resolve. If the victim complains of shortness of breath or wheezing, or has a swollen tongue (muffled voice) or lips, anticipate a more serious allergic reaction (see page 78). Be prepared to administer epinephrine (see page 484).

Hives can also be induced by exposure to cold or during rewarming of cold skin (cold urticaria). Accompanying the skin lesions can be fatigue, headache, shortness of breath, rapid heart rate, and, rarely, full-blown anaphylaxis (see page 78). Avoidance of cold might not be totally preventive, since the rate of cooling seems to be as important a factor as the environmental temperature. Avoidance of sudden temperature changes and cold exposure are advised. Certain drugs, such as cyproheptadine (Periactin), can be prescribed by a physician as treatment.

Hives might also be caused by exposure to water of any temperature (“aquagenic urticaria”). This can sometimes be prevented by greasing the skin with petrolatum ointment prior to water exposure or taking an antihistamine one hour before exposure.