Published estimates show that only three in 10 adults claim to routinely practice sun-protection behaviors1, while a recent study demonstrated that children's use of sunscreen diminishes as they age2. Whether this apathy is due to confusion surrounding the topic of sun protection, the allure of golden skin, or other factors is not quite clear. What these statistics do demonstrate, however, is the need to clarify and simplify the basic steps necessary to protect the skin from the negative effects of sun exposure – an obligation that is placed primarily on the shoulders of skin care professionals and those in the medical community.
While the body of research on the topic of sun protection is often contradictory, a number of best practices do emerge. However, before jumping into what to do to protect skin, it should first be explained to clients why sun exposure remains such a threat to human health and, of course, the aesthetics of our skin. Additionally, it is important for those of us counseling the public to be educated about several controversies related to sunscreen products.

The Dangers of UV Exposure
In addition to the light that we see, the sun emits ultraviolet (UV) rays of invisible radiation. There are three types of UV light:
UVA rays easily penetrate the earth's ozone layer and are, thus, the most prevalent type of UV light. UVA is responsible for our tanned appearance after sun exposure and remains generally consistent in intensity year-round. In fact, UVA can penetrate windows, signaling the need for sun protection habits to continue indoors. Because UVA is capable of reaching the dermis layer, it affects the production of collagen and elastin, thereby accelerating the signs of aging.
The majority of UVB rays are absorbed by the earth's ozone layer, so while they are certainly present, they are less prevalent than UVA. UVB rays are unable to penetrate windows, however. They reach the epidermis layer of the skin and are primarily responsible for the burning and redness that accompanies excessive sun or tanning bed exposure.
UVC rays are the most dangerous type of UV light. However, because UVC rays are absorbed by the earth's ozone layer, we are not at risk of exposure. Given they would be deadly to humans, this is a good thing.
While UVA is generally blamed for photoaging and UVB for sunburn, both damage the skin's cellular DNA, which can lead to skin cancer. In the case of melanoma, which accounts for only 10 percent of skin cancer but is responsible for at least 80 percent of skin cancer deaths3, researchers have speculated that UVA exposure is a more likely culprit than UVB rays. A 2010 study demonstrated that UVA radiation damages the DNA of melanocytes – the cells located in the bottom layer of the epidermis that produce melanin, thereby causing genetic mutations.4 Because melanocytes have a reduced capacity to repair this DNA damage, they mutate more frequently, a factor that can lead to melanoma.

Sunscreen Formulations
Because researchers originally believed that preventing sunburn was the optimal way to minimize the risk of photoaging and skin cancer, most sunscreens were formulated to protect solely against UVB. Today, however, in light of the body of research that illustrates the dangers of UVA exposure, there are an ever-increasing number of products available that filter out both UVA and UVB. These are marketed as "broad spectrum" sunscreens. Sunscreen formulations fall into two categories:
The first is sun block, which physically reflects or scatters UV light through the use of inorganic compounds that sit on the skin's surface. The active ingredients used in sun blocks are titanium dioxide, capable of reflecting UVB rays and some UVA rays, and zinc oxide, which offers broad-spectrum protection. While these ingredients are optimal from a protection standpoint, they were not so long ago characterized by a large drawback from an aesthetics point of view – they left an opaque, white residue on the skin. In recent years, nanotechnology has been used to reduce the particle size of zinc oxide and titanium dioxide, allowing them to be used in formulations without leaving a visible trace. This has made the use of products containing these ingredients far more appealing. Problem solved, right? Not so fast.
The use of nanotechnology in cosmetics has long been a hotly debated topic. Some experts believe that these minute nanoparticles are absorbed deep into the skin and enter the bloodstream, where, upon circulation throughout the body, they may cause genetic damage. However, of the numerous studies related to this topic, none have demonstrated a reliable cause for alarm. Rather, current research fails to demonstrate that nanoscaled UV filters penetrate living cells.5 Another concern is that when zinc oxide and titanium dioxide nanoparticles are applied to the skin, they create a mesh effect whereby UV light can penetrate between microscopic spaces. To avoid this potential, a chemical sunscreen is often added to the formulation as a backup. This brings us to the second sunscreen category.
Chemical sunscreen absorbs UV light and turns it into energy. Among the active ingredients most commonly used in these products are octyl methoxycinnamate, avobenzone (Parsol 1789), and oxybenzone. Active chemical sunscreen ingredients are often used in various combinations within a single formulation to ensure broad spectrum protection.
Of the 17 active sunscreen ingredients allowed by the FDA, some are plagued by controversy due to their organic nature. Para-aminobenzoic acid (PABA) was among the first active ingredients widely used in chemical sunscreens. However, PABA was reported to cause allergic reactions in some individuals and can stain clothing. Today, many sunscreen products tout their PABA-free status.
Oxybenzone, a broad-spectrum chemical sunscreen, is also a widely used active ingredient, but several research findings are impacting its popularity. Among them, oxybenzone has been shown to cause allergic reactions in some individuals6 and can be absorbed into the body.7 The concern is that, in certain circumstances, absorbed oxybenzone can react with the sun, causing the development of free radicals8 that could potentially lead to skin cancer. Despite this, "acute toxicity has not been reported in any of the in vivo or human studies published to date," according to a recent research review.9

Sun Protection Factor
The gold standard for determining the effectiveness of a sunscreen product has long been its SPF (Sun Protection Factor) rating, which relates only to the level of UVB protection it offers. Until now, SPF has referred to the amount of time it would take you to burn without sunscreen. (E.g. If you typically burn after 10 minutes in the sun, SPF 15 would protect you 15 times longer.) However, the FDA is implementing new requirements for over-the-counter sunscreen products.10 By June, sunscreen must be tested and labeled according to improved SPF and broad-spectrum test procedures, which measure the amount of UV exposure it takes to cause sunburn when the individual is using the product (SPF test), as well as its ability to protect against UVA exposure (broad-spectrum test). Products proven to offer UVA and UVB protection will now include the words "broad spectrum" on the label, along with the proper SPF rating according to the new criteria. Those that only protect against UVB rays will bear the warning, "Skin Cancer/Skin Aging Alert: Spending time in the sun increases your risk of skin cancer and early skin aging. This product has been shown only to help prevent sunburn, not skin cancer or early skin aging."
While we have traditionally seen a wide range of SPF ratings – from two to 100, the FDA is also placing a limit on these claims. We will soon only see SPF ranges from two to 50+. Those products with an SPF lower than 15 must include the above warning on the packaging.
The FDA's new requirements re-garding SPF are intended to make it easier for consumers to determine how much protection a product offers them. Even with the new regulations, however, a product's SPF rating is not necessarily a true reflection of the protection users are receiving. Studies have shown that sunscreen users typically apply insufficient sunscreen and neglect several prominently exposed skin sites.11 Thus, an education in the proper application technique is vital.
So what about selecting the proper SPF? Those individuals who have sought optimal sun protection have traditionally selected products with the highest ratings available. But is it necessary? Consider that SPF 15 filters out approximately 93 percent of UVB light, while SPF 30 filters out 97 percent. As you go up to SPF 100, approximately 99 percent of UVB light is filtered out. While more protection from harmful UVB rays is a good thing, keep in mind that sunscreen is not the be-all and end-all in a proper sun protection strategy. When using products with a higher SPF, individuals may feel a false sense of security that leads them to enjoy extended sun exposure in which they neglect to implement supplemental protective behaviors. Because some sunscreen products do not protect skin from UVA rays, this extended time in the sun could be threatening their health and, potentially, increasing their risk for melanoma.

The Vitamin D Debate
Vitamin D is essential to the body not only because it encourages bone strength, but also because of its role in decreasing the risk of many chronic illnesses, including common cancers, autoimmune diseases, infection disease and cardiovascular diseases.12 It is no wonder, then, that much has been made of the current vitamin D crisis. Vitamin D inadequacy has been reporter in approximately 36 percent of otherwise healthy young adults and up to 57 percent of general medicine inpatients in the U.S.13 Among the suspected reasons for this widespread deficiency is improper diet and, you guessed it – sunscreen usage.
Sun exposure triggers the body's synthesis of vitamin D. However, in blocking or filtering UV rays, it is believed that sunscreen inhibits the amount of vitamin D the body can produce. Is it reason enough to cease sunscreen use? Not at all. For one, the connection between sunscreen use and vitamin D deficiency has been called into question by more than one study. In one in particular, sunscreen users experienced just a minor decrease in vitamin D levels, but not enough to be labeled as a deficiency.14 And in another well-publicized study, it was demonstrated that vitamin D deficiencies occurred in 51 percent of a sample that received abundant exposure to sunlight.15 These studies, and others, leave open the possibility that other factors may be at work.

Conclusion
Despite the various debates focused on the topic of sunscreen, its use as an essential tool in the effort to encourage optimal skin health should not be diminished. Rather, clients should be encouraged to implement the best practices in sun protection, each of which takes into consideration the above topics:
Utilize a broad spectrum sunscreen. While formulations with zinc oxide and titanium dioxide are ideal for those with sensitive skin or prone to dermatitis, the general population should choose the product with which they feel most comfortable. Current research regarding sunscreen ingredients and technologies has not made a convincing case for abandoning any of the currently FDA-approved FDA active sunscreen ingredients. Therefore, helping clients find a product they will use regularly should be the goal.
All individuals, regardless of skin color, should apply sunscreen with an SPF of 15 or 30 on a daily basis, regardless of the weather or the season. To ensure adequate protection, it should be applied 15 to 20 minutes before going outdoors and reapplied often throughout the day to ensure continuous protection while minimizing the risk of free radical damage.
Average sized adults should apply one ounce of sunscreen – or the amount equivalent to a shot glass – evenly to all exposed areas of body. Those smaller or larger must adjust this amount accordingly. While sunscreen lasts approximately three years, if applied in the appropriate manner, a bottle should not last more than a season.
Get, at most, approximately 15 minutes of unprotected sun exposure twice a week to encourage vitamin D synthesis. This recommendation should be reduced for those who burn easily.
Utilize sunscreen as just one element of the sun protection routine. Remember to wear protective clothing and hats whenever you go outdoors. During extended outdoor activity, seek shade regularly. Be mindful of when you go outdoors and the length of sun exposure.

I expect we will continue to learn much more about these and many other sunscreen topics in the coming years, as product technology and ingredient research continues to evolve. Regardless of the controversies these products face, however, their benefits far outweigh the risks. Because of this, our message to clients and the public at-large should simply be: Do not forget the sunscreen.

Sources:
1 Buller DB, Cokkinides V, Hall HI, et al. Prevalence of sunburn, sun protection and indoor tanning behaviors among Americans: Review from national surveys and case studies of 3 states. J Am Ac Derm. 2011;65(5):S114-S123
2 Dusza SW, Halpern AC, Satagopan JM, et al. Prospective study of sunburn and sun behavior patterns during adolescence. Pediatrics. 2012;129(2):309-17.
3 Ibanez IL, Notcovich C, Policastro LL, Duran H. Reactive oxygen species in the biology of melanoma. In: Tanaka Y, ed. Breakthroughs in Melanoma Research. InTech; 2011.
4 Wang HT, Choi B, Tang MS. Melanocytes are deficient in repair of oxidative DNA damage and UV-induced photoproducts. Proc Natl Acad Sci. 2010;107(27):12180-12185
5 Burnett ME, Wang SQ. Current sunscreen controversies: a critical review. Photoderm, Photoimm & Photomed. 2011;27:58-67.
6 Szczurko C, Dompmartin A, Michel M, Moreau A, Leroy D. Photocontact allergy to oxybenzone: ten years of experience. Photoderm Photoimm Photomed. 1994;10(4):144-7
7 Calafat AM, Wong LY, Ye X, Reidy JA, Needham LL. Concentrations of the sunscreen agent benzophenone-3 in residents of the United State: National Health and Nutrition Examination Survey 2003-2004. Environ Health Perspec. 2008;116(7):893-7.
8 Hanson KM, Gratton E, Bardeen CJ. Sunscreen enhancement of UV-induced reactive oxygen species in the skin. Free Rad Bio Med. 2006; 41(8):1205-12.
9 Burnett ME, Wang SQ. Current sunscreen controversies: a critical review. Photoderm Photoimm Photomed. 2011; 27(2):58-67.
10 http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm258416.htm
11 Azurdia RM, Pagliaro JA, Rhodes LE. Sunscreen application technique in photosensitive patients: a quantitative assessment of the effect of education. Photoderm Photoimm Photomed. 2000;16:53-6.
12 Holick MF. Vitamin D Deficiency. N Engl J Med. 2007;357:266-81.
13 Holick MF. High prevalence of vitamin D inadequacy and implications for health. Mayo Clin Proc. 2006;81(3):353-73.
14 Farrerons J, Barnadas M, Rodriguez J, et al. Clinically prescribed sunscreen (sun protection factor 15) does not decrease serum vitamin D concentration sufficiently either to induce changes in parathyroid function or in metabolic markers. Br J Derm. 1998;139(3):422-7.
15 Binkley N, Novotny R, Krueger D, et al. Low vitamin D status despite abundant sun exposure. J Clin Endoc Metab. 2007;92(6):2130-35.

Dr. Ahmed Abdullah, a board-certified plastic and cosmetic surgeon, is CEO and co-founder of Lexli International, Inc. A recognized expert on the restorative and medicinal effects of aloe vera, he has authored several published studies about its healing potential. Abdullah is the chief formulator of the Lexli® line of aloe-based skin care, including the company's flagship product, AloeGlyC Renewing Exfoliant®. He is a member of the International Aloe Science Council (IASC) based in Dallas, Texas, and has served on its board of directors. Abdullah is married to Dr. Kay Abdullah, a board-certified surgeon and co-founder of Lexli International, Inc. They have two sons – Alex and Ali – whose names were combined to form the Lexli brand name.