Chapter 49 Sunscreens and prevention of skin cancer
1. List some of the important facts about skin cancer.
• In the United States, over 1 million new cases of skin cancer are diagnosed annually, afflicting more people than any other cancer.
• In 2009, according to the American Cancer Society, 68,720 Americans will develop malignant melanoma, and there will be 8,650 melanoma-related deaths.
• Melanoma accounts for about 4% of skin cancer cases, but it causes about 79% of skin cancer deaths.
• The incidence of melanoma is increasing at a rate faster than that of any other cancer, having nearly doubled in the last decade.
American Academy of Dermatology. Available at: http://www.aad.org. Accessed August 3, 2010.
American Cancer Society. Available at: http://www.cancer.org. Accessed August 3, 2010.
Skin Cancer Foundation. Available at: http://www.skincancer.org. Accessed August 3, 2010.
2. How does skin type affect the risk for skin cancer?
Anyone can get skin cancer, although some people are at greater risk than others. The skin phototype (SPT) system was developed to identify people who are prone to develop skin cancer. The SPT system is a six-point scale based on a person’s skin color and ability to tan (Table 49-1). Individuals who fall into SPT groups I and II are at highest risk for the development of skin cancer. These two groups of people are especially prone to develop basal cell and squamous cell carcinoma and are at high risk for developing melanoma. Skin types III and IV are less prone to develop basal cell and squamous cell carcinoma but are still at risk for developing melanoma. Basal cell carcinoma, squamous cell carcinoma, and melanoma are rare in skin types V and VI. If patients in groups V and VI develop melanoma, it usually occurs on the palms and soles (acrolentiginous melanoma) or on mucosal surfaces, such as in the mouth or on the genitalia.
3. What are the other risk factors for skin cancer?
Strong skin cancer risk factors include family history, total cumulative sun exposure, the number of blistering sunburns, multiple atypical moles, immunosuppression, and occupational exposure to coal tar, pitch, creosote, arsenic compounds, or radium. Lifetime cumulative sun exposure directly correlates with basal cell and squamous cell carcinoma risk. Individuals who are exposed to the sun on a daily basis, such as farmers, fishermen, and construction workers, are at high risk for developing nonmelanoma skin cancer. Sunburns are directly related to melanoma risk. One study reported a 2.5- to 6.3-fold increased melanoma risk for a person with a history of three or more blistering sunburns. For this reason, indoor workers such as health care professionals and office workers who experience intense, intermittent sun exposure are more prone to developing melanoma.
4. Do hereditary factors affect skin cancer risk?
Skin cancer appears to have a hereditary component. The prototype syndrome of genetically determined increased skin cancer risk is xeroderma pigmentosum (XP). XP patients suffer from an autosomal recessive defect in DNA repair that results in sun sensitivity and early onset of basal cell carcinoma, squamous cell carcinoma, and melanoma. Although much of the molecular genetics of XP is understood, further study is necessary to better understand the genetics of other types of skin cancer-prone families. However, a useful recommendation is to have all first-degree relatives (parents, siblings, and children) of a skin cancer patient examined for skin cancer and taught sun-protection measures.
5. What age or sex factors are important in skin cancer risk?
• Basal cell and squamous cell carcinoma incidences peak in the seventh decade of life. Melanoma incidence peaks around age 50.
• Overall, men develop more skin cancer than do women, but in the third and fourth decades of life, almost as many women develop skin cancer as men.
• Melanoma occurs most frequently on the chest, shoulders, and back in males and in young women (ages 15 to 29). Melanoma is most commonly found on the legs of adult women 30 years and older.
7. What warning signs of possible skin cancer should be looked for in the self-skin exam?
The self-skin exam is an important part of skin cancer prevention for two reasons: Studies have shown that abnormal skin lesions are frequently discovered first by the patient, and skin cancer, when treated early, is curable. Patients should be encouraged to examine their entire skin surface on a monthly basis, remembering to include the scalp and normally non–sun-exposed sites, including the buttocks, genitalia, and feet. Warning signs of a possible skin cancer include
8. How is ultraviolet light classified?
Ultraviolet (UV) light is broken down into bands of light according to its physical characteristics and biologic effects:
• UVC: 100 to 290 nm wavelength. High-energy radiation that injures cells through direct DNA damage and the generation of free-radical species. Fortunately, UVC radiation is filtered by atmospheric ozone and does not reach the earth’s surface.
• UVB: 290 to 320 nm wavelength. Midrange radiation that is not completely filtered by atmospheric ozone, called the “burning” rays because it causes sunburn. UVB injures skin cells primarily through formation of DNA thymine dimers and 6 to 4 photoproducts that, if not repaired properly, cause gene mutations and lead to altered cell function and carcinogenesis.
• UVA: 320 to 400 nm wavelength. Long-wave radiation that is the lowest energy spectrum of ultraviolet. UVA is not filtered by atmospheric ozone, and a 150-fold greater amount of UVA strikes the surface of the earth compared to UVB. UVA damages skin cells predominantly through the formation of free radicals. UVB penetrates to the basal layer of the epidermis, whereas UVA penetrates to the middermis. Skin wrinkling following chronic sun exposure is due to UVA injury of dermal fibroblasts, resulting in altered collagen and elastin synthesis.
| SKIN PHOTOTYPE* | UNEXPOSED SKIN COLOR | SUN RESPONSE HISTORY |
|---|---|---|
| I | White | Always burns, never tans |
| II | White | Always burns, tans minimally |
| III | White | Burns minimally, tans gradually and uniformly |
| IV | Light brown | Burns minimally, always tans well |
| V | Brown | Rarely burns, tans darkly |
| VI | Dark brown | Never burns, tans darkly |
* Based on the first 30 to 60 minutes of sun exposure of untanned skin after the winter season.
Key Points: Health Benefits of Solar Radiation
2. Skin exposure to ultraviolet B is necessary for the conversion of 7-dehydrocholesterol into previtamin D3, which then isomerizes to vitamin D3.
9. List the 13 basic facts regarding sun protection.
1. Sun damage is cumulative. Each dose of ultraviolet radiation (UVR), large and small, adds up, leading to skin wrinkling, dyspigmentation, and skin cancer.
3. Avoid sun exposure between the hours of 10 am and 2 pm (11 am to 3 pm daylight savings time), when UVB is most intense. Plan outdoor activities for early morning or late afternoon.
5. Beware of high-altitude sun exposure, where there is less (thinner) atmosphere to absorb UVR, and therefore the risk of sunburn is greater.
7. Use protective clothing and apply sunscreens even on overcast days. Although UVR is less intense on overcast days, it is still present and adds to cumulative skin damage.
8. UVR is reflected off of sand, concrete, and snow and adds to the total UVR exposure. Because UVR is reflected and scattered, sitting in the shade is not totally protective and sunburn can occur.
9. Do not use tanning beds. Although tanning beds emit primarily UVA, overexposure can cause sunburn, and their use enhances skin aging and the risk for skin cancer.
10. People at high risk for skin cancer (persons with skin types I and II, outdoor workers, and persons with a history of skin cancer or a photosensitivity disorder) should apply sunscreens daily.
11. Some medications (sulfonamides, tetracyclines, and birth control pills, as well as over-the-counter products) and cosmetic ingredients (lime oil) can be photosensitizing.
10. What type of clothing is considered sun-protective?
12. Compare the advantages and disadvantages of the physical and chemical sunscreens.
Physical sunscreens are agents that scatter and reflect UVR, while chemical sunscreens absorb UVR through a photochemical reaction. Physical sunscreens include zinc oxide and titanium dioxide and have advantages over chemical sunscreens. Physical sunscreens are inert, they do not break down over time, and they do not cause contact dermatitis or photodermatitis. They block both UVB and UVA (Table 49-2). However, physical sunscreens have one drawback: they leave a slight makeup base appearance to the skin that some people find unappealing.
Table 49-2. Sunscreens That Block UVB and UVA
| PRODUCT NAME | SPF | MANUFACTURER |
|---|---|---|
| Aveeno Continuous Protection | 30, 50, 55, 70 | Johnson and Johnson |
| Aveeno Baby | 55 | Johnson and Johnson |
| Banana Boat | 15, 30, 50 | Sun Pharmaceutical |
| Bull Frog | 36, 50 | Chattem |
| Clinique Sunblock | 15, 30, 45, 50 | Clinique |
| Coppertone Water Babies | 50, 70 | Schering-Plough |
| Coppertone Nutrashield | 30, 70 | Schering-Plough |
| Coppertone Sport | 15, 30, 50, 70 | Schering-Plough |
| Estee Lauder | 15, 30 | Estee Lauder |
| Hawaiian Tropic Shear Touch | 15, 30, 50 | Tanning Research |
| Hawaiian Tropic Ultimate | 55, 70, 80 | Tanning Research |
| Hawaiian Tropic Baby Faces | 50, 60 | Tanning Research |
| Neutrogena Ultra Sheer | 55, 70, 85 | Neutrogena |
| Neutrogena Sensitive Skin | 30 | Neutrogena |
| Neutrogena Baby | 60 | Neutrogena |
| No-Ad | 15, 30, 45 | Sun and Skin Care Research |
| No-Ad Babies | 50 | Sun and Skin Care Research |
| Pre Sun | 27, 30 | Bristol Myers |
| Mary Kay Sunscreen | 15, 30 | Mary Kay |
| Vanicream Sunscreen Sport | 35 | Pharmaceutical Specialties |
14. What factors should be considered in selecting a sunscreen?
• The sunscreen should block both UVB and UVA and have a sun protection factor (SPF) rating of 15 or greater.
15. How is an SPF determined?
Sunscreen SPF is defined as the ratio of the minimal dose of sunlight needed to cause redness of sunscreen-protected skin divided by the minimal dose of sunlight needed to cause redness of unprotected skin. SPFs of 15, 30, and 50 effectively reduce UV skin absorption by 94%, 97%, and 98%, respectively.
16. How much sunscreen should be applied? How often should it be reapplied?
Warn your patients that most people apply too little sunscreen. To cover the face, arms, legs, and upper torso of an average-sized adult requires 1 ounce of sunscreen, which is generally a handful. A smaller person or child needs proportionally less. Sunscreen should be applied evenly and rubbed into all exposed skin. It should be applied 30 to 60 minutes before sun exposure. Then a second layer should be applied at the beginning of sun exposure and, under normal conditions, reapplied every 2 hours. Sunscreen should be reapplied more often if swimming, sweating, or rubbing has removed some of the product. Warn patients that reapplication does not double the SPF and to not rely on redness as a signal to reapply sunscreen. Skin damage occurs before sunburn appears.
17. Can sunscreens be safely used in children?
Yes. Most major cosmetic and pharmaceutical companies make sunscreen products for children. All recommendations for sunscreen use in adults should be followed for children. However, sunscreens need not be used in children less than 6 months of age. Any child who has not yet learned to crawl should be protected with long sleeves, long pants, and a hat and should be kept away from direct sunlight.
18. Why are sunglasses included in sun-protection recommendations?
Sunglasses protect the eyelids, sclera, cornea, and lens from UVR injury. Intense, acute UVR eye injury results in sunburn of the eyelids, sclera, and cornea, whereas chronic sun exposure causes cataracts and skin cancer of the periorbital skin. Patients should be instructed to buy sunglasses that absorb UVB and UVA. Also, a large frame area better protects the skin around the eyes.
19. Are tanning pills safe to use?
Not entirely. Canthaxanthin, the active ingredient in most tanning pills, is not approved by the U.S. Food and Drug Administration. While most patients do not have significant side effects, some patients have developed nausea, diarrhea, pruritus, skin eruptions, night blindness, and drug-induced hepatitis. There has been one reported death due to aplastic anemia in a woman who took tanning pills.
21. What is the relationship between UVR, the skin, and vitamin D?
Two primary sources of vitamin D are the diet and cutaneous UVB exposure. The inactive form of vitamin D (7-dehydrocholesterol) contained within epidermal keratinocytes is converted photochemically by UVB radiation to previtamin D3. Previtamin D3 then spontaneously isomerizes to vitamin D3 (3-cholecalciferol). Vitamin D3 is then hydroxylated by the epidermis and the liver to 25-hydroxy vitamin D3, which is then further hydroxylated to the active form 1,25-hydroxy vitamin D3 or calcitriol.
| CHEMICAL | MAXIMUM CONCENTRATION USED (%) |
|---|---|
| Aminobenzoic acid | 15 |
| Avobenzone | 3 |
| Cinoxate | 3 |
| Dioxybenzone | 3 |
| Homosalate | 15 |
| Menthyl anthranilate | 5 |
| Octocrylene | 10 |
| Octyl methoxycinnamate | 7.5 |
| Octyl salicylate | 5 |
| Oxybenzone | 6 |
| Octyl dimethyl PABA | 8 |
| Phenylbenzimidazole sulfonic acid | 4 |
| Sulisobenzone | 10 |
| Titanium dioxide | 25 |
| Trolamine salicylate | 12 |
| Zinc oxide | 25 |
22. If UVB is required for vitamin D metabolism, how would one maintain normal vitamin D levels with restricted sun exposure? How much sun exposure is necessary?
In the southern United States, daily short UVB exposure (5 minutes for lightly pigmented people and 10 minutes for darkly pigmented people) of a small area of skin (face, hands, and arms) will supply ample vitamin D for the body’s needs. However, at latitudes greater than 40 degrees, winter sun exposure does not produce active vitamin D. Therefore, residents of the northern United States should take supplemental vitamin D of at least 400 IU daily. Fortunately, proper vitamin D levels can be easily maintained by eating a vitamin D–fortified diet. Eggs, beef liver, and oily fish, such as salmon, catfish, herring, mackerel, and tuna, are excellent sources of vitamin D. Many foods, such as milk, cereals, and bread are fortified with vitamin D, and most multivitamins contain vitamin D.
Weinstock MA, Moses AM: Skin cancer meets vitamin D: the way forward for dermatology and public health, J Am Acad Dermatol 61(4):720–724, 2009.
23. What is proper sunburn treatment?
Take aspirin or ibuprofen as soon as sunburn is detected to help reduce inflammation and control pain. Tylenol helps control pain but is not antiinflammatory. Cool, wet compresses, or tub soaks for 20 minutes, four or five times daily will help with pain control. Do not use butter or heavy ointments, because they can cause skin irritation, and do not use benzocaine sprays, because they can cause contact dermatitis. Light creams and lotions containing pramoxine will soothe the skin and reduce pain. Increased fluid loss can occur through sunburned skin. Therefore, fluid replenishment with an isotonic sport drink is recommended. Because sun-damaged skin is more susceptible to subsequent burns, sun exposure should be avoided until the skin completely heals in 1 to 2 weeks.
