[ Oncology Watch] Sun Protection: What We and Our Patients Need to Know To preserve their health and the appearance of their skin, patients need straight- forward, practical advice on susncreen selection and protection strategies. By Jonathan Wolfe, MD rom preventing skin cancer to pre- measures protection against cutaneous burning. Even a FDA public education serving a youthful appearance, burning—the effects of UVB—and does piece states, “A higher number means it Fsunscreens play an important role not account for UVA radiation at all.5 As protects longer.”7 This is not a strictly in dermatologic care. However, some a result, a product with a high SPF could accurate interpretation of the SPF value confusion persists among patients and actually confer little or no protection and ignores the fact that unique proper- even some practitioners when it comes to against UVA. ties of the main sunscreen ingredients SPF, available chemical and physical sun- The somewhat esoteric description of (chemical or physical) and the formula- screens, and the best advice for sun SPF calculation is available online at the tion (waterproof, water resistant) influ- avoidance. In recognition of the AAD’s FDA website.6 Ultimately, the SPF num- ence duration of protection. Skin Cancer Detection and Prevention ber represents the ratio of the MED for Patients also often falsely assume that Month, I’ll review important patient protected skin (MED(PS)) to the MED the increase in SPF value is proportion- education points. for unprotected skin (MED(US)). Tests ate to the increase in UVB protection. It are conducted only in patients with skin is not. A product with SPF 30 does not Understanding SPF types I-III, and the applied MED(PS) block twice the amount of UVB as a The non-scientific explanation of radia- ranges from 0.64 to 1.56 times the product with SPF 15. In actuality, an tion is that UVA contributes significantly MED(US) depending on skin type. SPF 30 product may filter out less than to aging while UVB is responsible for A common belief among patients is 97 percent of UVB, while SPF 15 may burns. Scientific evidence supports these that the SPF number reflects a time fac- filter out more than 93 percent. observations but shows the reality is far tor—the higher the number the more Because SPF value only addresses the more complex. UVB levels, which are time one can spend outdoors without UVB protection a product confers, der- relatively low compared to UVA, pene- trate the superficial epidermal layers, UV-C UV-B UV-A where the absorbed energy produces ery- thema and can induce cellular damage Aminobenzoic acid (PABA) that may lead to skin cancer formation.1,2 Padimate O UVA radiation penetrates more deeply, Dioxybenzone Oxybenzone through most clothing and into the epi- Sulisobenzone dermis and dermis. UVA has long been MenthylAnthranilate 4 associated with melanoma risk (the Avobenzone (Parsol 1789) mechanism remains unclear), and recent Cinoxate research suggests that it also plays a role Octylmethoxycinnamate in the development of squamous cell and Octocrylene basal call carcinomas.3 In addition to Homosalate causing direct damage to cells, UVA radi- Trolamine salicylate ation is linked to free-radical generation. Octyl salicylate While both UVA and UVB radiation Table 1. UV Absorption Spectrum Phenylbenzimidazole sulfonic acid are associated with skin cancer risk, the Titanium dioxide sun protection factor or SPF scale used Zinc oxide to rate sunscreen formulations only Adapted from www.solumedia.com/sunscreen3.htm Wavelength in nm 200 220 240 260 280 300 320 340 360 380 400 56 Practical Dermatology May 2005 [ Oncology Watch] matologists now recommend that chemical for UVB protection. Table 1 over the Internet. An Australian study is patients look for and use only “broad- lists UV protective absorption spectrums underway to assess the benefit of such spectrum” sunscreen products. To help of most approved sunscreen ingredients. clothing. There is even a laundry additive patients make wise product choices, we Some confusion exists regarding water (Sun Guard) that increases the UV must explain SPF to them and offer resistance of sunscreen products. The blocking ability of clothes. Some beach some advice on identifying and choosing label SPF of a “water resistant” product is umbrellas may permit a fair amount of the most effective ingredients. the SPF calculated after application and UVR to pass through. Patients can pur- subsequent exposure to water for 40 chase umbrellas and canopies made from Physical and Chemical Blocks minutes. The label SPF of a “very water UVR-reflecting materials. The ingredient with the widest protec- resistant” product is the SPF after 80 Finally, when asking patients to aban- tive absorption spectrum available in the minutes. Note that in both assays, sub- don a bad habit, such as tanning, it helps US is micronized zinc oxide (ZnO) or Z- jects air dry after emerging from the to offer alternatives. UV-free tanning Cote, which offers absorption from water but before enduring UV irradia- with DHA sprays and lotions is a safe about 250nm to 400nm. As a physical tion; they do not towel off. In reality, alternative that may be worth consider- sunscreen, ZnO sits on the skin to create patients who towel off theoretically ing.9 A recent study revealed that college a reflective barrier against UVR, whereas remove at least some sunscreen product. students who received education about chemical sunscreens absorb into the skin. photoaging, UV photographs, and access At concentrations of 3.5% or more, Beyond Sunscreens to sunless tanning engaged in greater sun micronized ZnO confers good broad- Beyond helping patients decide which protection behaviors than controls or spectrum protection. Nonetheless, it is sunscreens to use, offer directions on those who received education and pho- often formulated with other physical and how to properly use it. Stress the need tography alone.10 chemical sunscreens to enhance protec- to apply sunscreen 15 minutes before tion. Zinc oxide is very water resistant. exposure to sunlight and the need to A Skin Wellness Program Like zinc oxide, titanium dioxide apply it to all sun exposed skin. Depending on your particular patient (TiO2) is also a broad-spectrum physical Patients easily forget the hands, ears, base or practice focus, you may sunscreen, but its absorption spectrum back of the neck, and the feet. Esti- encounter individuals who are as inter- (260-360nm) does not extend as far into mates suggest that patients generally ested in reversing already apparent the UVA range. Even as a microfine par- apply about one third the recommend- photo-damage as they are in preventing ticle, TiO2 may produce a whitish ed amount of sunscreen to their skin additional injury. Be receptive to residue when applied to the skin. (2mg/cm2 of skin surface area). patients’ skin care concerns when dis- Parsol 1789 or avobenzone is another As we continue to stress sunscreen cussing sunscreens. popular sunscreen ingredient. This use, we must also offer patients practical For patients with mild to moderate chemical sunscreen absorbs across the advice about sun avoidance and sun-pro- photodamage, topical retinoids are an full UVA spectrum but confers no UVB tection tactics. Patients should avoid obvious choice for inclusion in the regu- protection. It must be combined with direct sunlight as much as possible, espe- lar skincare regimen. Beyond their role in UVB blocking ingredients to confer full- cially during midday, and should not use diminishing fine lines and wrinkles and spectrum UVR protection. There’s con- UV tanning lamps and beds. There’s a evening skin tone, topical retinoids influ- troversy regarding the photostability of persistent myth, promulgated to some ence cell differentiation and can block avobenzone with some reports (but no extent by the tanning salon industry, that proliferation of malignant cells. accessible published studies) suggesting a “base tan” can be protective. Tell For patients with very mild signs of that the agent degrades upon exposure to patients this is false. photodamage, a cosmeceutical product UVR. A 1996 study in Journal of Apparel, including broad-brimmed may be appropriate based on your assess- Chromatography BioMedical Applications hats and scarves, can be protective, but ment of the product and its efficacy. reportedly showed that the concentration patients may not realize that UVR, par- Note that there’s continuing research of avobenzone in a sample decreased by ticularly UVA, can penetrate many fab- into the incorporation of topical antioxi- just 25 percent following 72 hours of rics, particularly cotton weaves and wet dants within sunscreens to offer protec- sun exposure. clothing. Specially-woven and treated tion and reversal of oxidative stress. Oxybenzone is another UVA screen, fabrics that reflect both UVA and UVB However, there’s no evidence that any though its absorption range is relatively radiation are used to make swimsuits, available product formulated with narrow. Octyl methoxycinnamate is every-day clothing, and hats. Many antioxidants confers additional benefit probably the most commonly used brands and styles are available, many over standard sunscreens. May 2005 Practical Dermatology 57 [ Oncology Watch] Oct;15(5):316-20. 6. Code of Federal Regulations, Title 21, Volume 5, Assume Nothing 2. van Weelden H, van der Putte SC, Toonstra J, van der Revised as of April 1, 2004. To help patients protect themselves from Leun JC. Ultraviolet B-induced tumors in pigmented hair- 7. http://www.fda.gov/opacom/lowlit/sunsafty.html less mice, with an unsuccessful attempt to induce cuta- 8. www.cosmeticscop.com skin cancer, we must offer clear advice neous melanoma. Photodermatol Photoimmunol Photomed. 1990 Apr;7(2):68-72. 9. Levy SB. Tanning preparations. Dermatol Clin. 2000 on sunscreen selection, stress the need for Oct; 18(4):591-6.