The Medical Letter on Drugs and Therapeutics Volume 60 ISSUE ISSUE No. 1433 1553 Volume 56 IN THIS ISSUE Sunscreens...p 129 Important Copyright Message FORWARDING OR COPYING IS A VIOLATION OF U.S. AND INTERNATIONAL COPYRIGHT LAWS The Medical Letter, Inc. publications are protected by U.S. and international copyright laws. Forwarding, copying or any distribution of this material is prohibited. Sharing a password with a non-subscriber or otherwise making the contents of this site available to third parties is strictly prohibited. By accessing and reading the attached content I agree to comply with U.S. and international copyright laws and these terms and conditions of The Medical Letter, Inc. For further information click: Subscriptions, Site Licenses, Reprints or call customer service at: 800-211-2769 Published by The Medical Letter, Inc. A Nonprofit Organization medicalletter.org
The Medical Letter publications are protected by US and international copyright laws. Forwarding, copying or any other distribution of this material is strictly prohibited. For further information call: 800-211-2769 The Medical Letter on Drugs and Therapeutics Volume 60 Take CME Exams Sunscreens Excessive exposure to ultraviolet (UV) radiation is associated with sunburn, photoaging, and skin cancer. 1,2 Sunscreens are widely used to reduce these risks, but some questions remain about their effectiveness and safety. UVA and UV radiation capable of injuring the skin is classified based on wavelength as UVA1 (340-400 nm), UVA2 (320-340 nm), and (290-320 nm). UVA, which makes up 95% of terrestrial UV radiation, penetrates the dermis and causes long-term damage., which is mostly absorbed in the epidermis, is largely responsible for the erythema of sunburn. Both UVA and can cause photoaging and skin cancer. is strongest at midday and is present primarily in late spring, summer, and early autumn in temperate climates. UVA is constant throughout the day and the year and, unlike, is not filtered by clear glass. SPF Sun Protection Factor (SPF) is the ratio of the time required to develop a minimally detectable sunburn while wearing a sunscreen product to the time required without wearing the product. It represents the fraction of erythema-producing UV light (primarily ) that penetrates through the product to reach the skin. When properly applied, an SPF 15 sunscreen allows penetration of 1/15th (7%) of erythemogenic UV photons, an SPF 50 sunscreen transmits 1/50th (2%), and an SPF 100 sunscreen transmits 1/100th (1%). Accordingly, SPF 50 and 100 sunscreens are only moderately more protective than SPF 15 sunscreens: 98% or 99% vs 93%. There is no specific rating system in the US for the amount of UVA protection provided by a sunscreen. The FDA allows sunscreens to be labeled "broadspectrum" if they provide UVA and protection and the UVA protection is proportional to the protection. Broad-spectrum sunscreens with an SPF 15 can claim that they can reduce the risk of skin cancer and early skin aging if used as directed with other sun protection measures. The FDA and the US Preventive Services Task Force (USPSTF) both recommend use of a broad-spectrum sunscreen with an SPF 15. 3,4 The American Academy of Dermatology recommends use of a product with an SPF 30. 5 SUNSCREEN ACTIVE INGREDIENTS Organic Several organic (chemical) sunscreens that absorb different wavelengths of UV light are approved by the FDA (see Table 1). Avobenzone is an effective UVA1 absorber and also absorbs some UVA2, but its efficacy decreases by about 60% after 60 minutes of exposure to sunlight due to photolability; the photostability of avobenzone is improved by combining it with other photostable UV filters. Octinoxate is a potent Table 1. FDA-Approved Sunscreens Sunscreen UV Protection Organic PABA Derivatives PABA (para-aminobenzoic acid) Padimate O (octyl dimethyl PABA) Cinnamates Cinoxate Octinoxate (octyl methoxycinnamate) Salicylates Homosalate Octisalate (octyl salicylate) Trolamine salicylate Benzophenones Dioxybenzone (benzophenone-8), UVA2 Oxybenzone (benzophenone-3), UVA2 Sulisobenzone (benzophenone-4), UVA2 Others Avobenzone (butyl methoxydibenzoyl UVA1 1 methane, Parsol 1789) Ecamsule 2 (terephthalylidene dicamphor, UVA2 sulfonic acid) Ensulizone (phenylbenzimidazole sulfonic acid) Meradimate (menthyl anthranilate) UVA2 Octocrylene Inorganic Titanium dioxide, UVA2, UVA1 Zinc oxide, UVA2, UVA1 = 290-320 nm; UVA2 = 320-340 nm; UVA1 = 340-400 nm; 1. May also provide UVA2 protection. 2. Meroxyl SX, patented by L'Oreal. Published by The Medical Letter, Inc. A Nonprofit Organization medicalletter.org 129
Table 2. Some Sunscreen Products 1 Product 2 Formulation Active Ingredients UV Protection Cost 3 SPF 15 Anthelios SX SPF 15 Cream Avobenzone 2%, ecamsule 4 2%, octocrylene 10% /UVA2/UVA1 $34.00 (La Roche-Posay) (3.4 oz) Badger Active SPF 15 Cream Zinc oxide 10% /UVA2/UVA1 13.60 (W.S. Badger) (2.9 fl oz) Banana Boat Protective Dry Spray Avobenzone 1.5%, homosalate 5%, octocrylene 3.5% /UVA1 5 10.99 Oil SPF 15 (Edgewell) Coppertone Sport SPF 15 Spray Avobenzone 2%, octisalate 4.5%, octocrylene 7% /UVA1 5 11.49 (Bayer) Hawaiian Tropic Sheer Touch Lotion Avobenzone 1.5%, homosalate 3%, octisalate 4.5%, /UVA1 5 11.79 SPF 15 (Edgewell) (8.0 fl oz) octocrylene 3% No-Ad SPF 15 (No-Ad) Lotion Avobenzone 1.2%, homosalate 7.5%, octisalate 5% /UVA1 5 7.57 (16 fl oz) Panama Jack SPF 15 Spray Octinoxate 5%, octisalate 3%, oxybenzone 2% /UVA2 10.99 (Panama Jack) Sun Bum 15 (Sun Bum) Lotion Avobenzone 2%, homosalate 5%, octisalate 2%, /UVA2/UVA1 16.00 (8.0 fl oz) octocrylene 1.85%, oxybenzone 3% SPF 30(+) Australian Gold Botanical SPF 30 Lotion Titanium dioxide 3%, zinc oxide 3% /UVA2/UVA1 12.99 (Australian Gold) (5.0 fl oz) Aveeno Active Naturals Lotion Avobenzone 3%, homosalate 8%, octisalate 4%, /UVA2/UVA1 11.99 Protect + Hydrate SPF 30 (3.0 fl oz) octocrylene 4%, oxybenzone 5% (Johnson & Johnson) Badger Sport SPF 35 Cream Zinc oxide 22.5% /UVA2/UVA1 13.60 (W.S. Badger) (2.9 fl oz) Banana Boat Sport Performance Spray Avobenzone 1%, octocrylene 7.7%, oxybenzone 3% /UVA2/UVA1 9.99 SPF 30 (Edgewell) Blue Lizard Australian Regular Lotion Octinoxate 7.5%, octocrylene 2%, oxybenzone 3%, /UVA2/UVA1 22.99 SPF 30+ (Crown) (8.75 fl oz) zinc oxide 6% Coppertone Sport SPF 30 Spray Avobenzone 3%, octisalate 4.5%, octocrylene 7%, /UVA2/UVA1 10.49 (Bayer) oxybenzone 4% Kiss My Face Sun Spray Lotion Lotion Octinoxate 7.5%, octisalate 5%, zinc oxide 1.7% /UVA2/UVA1 13.69 SPF 30 (Kiss My Face) (8.0 fl oz) Neutrogena Cool Dry Sport Spray Avobenzone 3%, homosalate 8%, octisalate 5%, /UVA2/UVA1 11.49 SPF 30 (Neutrogena) (5.0 fl oz) octocrylene 4%, oxybenzone 5% SPF 50(+) Anthelios SPF 60 Melt-In Milk Lotion Avobenzone 3%, homosalate 10.72%, octisalate 3.21%, /UVA2/UVA1 36.00 (La Roche-Posay) (5.0 fl oz) octocrylene 6%, oxybenzone 3.86% Babyganics SPF 50+ Spray Zinc oxide 11.2%, octinoxate 7.5%, octisalate 5% /UVA2/UVA1 11.99 (Babyganics) Banana Boat Kids Sport SPF 50+ Lotion Titanium dioxide 4.5%, zinc oxide 6.5% /UVA2/UVA1 11.49 (Edgewell) (6 fl oz) Banana Boat Sun Comfort Spray Avobenzone 3%, homosalate 10%, octisalate 5%, /UVA2/UVA1 11.49 SPF 50+ (Edgewell) (5.0 fl oz) octocrylene 3%, oxybenzone 4% Bull Frog Land Sport Quik Gel Gel Avobenzone 3%, homosalate 15%, octisalate 5%, /UVA2/UVA1 12.49 SPF 50 (Chattem) (1.5 oz) octocrylene 10%, oxybenzone 6% Coppertone Kids Tear Free Lotion Octinoxate 7.5%, octisalate 5%, zinc oxide 14.5% /UVA2/UVA1 12.49 SPF 50 (Bayer) Neutrogena Beach Defense Stick Avobenzone 3%, homosalate 15%, octisalate 5%, /UVA2/UVA1 11.49 Water + Sun Protection Stick (1.5 oz) octocrylene 10%, oxybenzone 3% SPF 50+ (Neutrogena) No-Ad Sport Stick SPF 50 Stick Avobenzone 3%, homosalate 10%, octisalate 5%, /UVA2/UVA1 6.99 (1.5 oz) octocrylene 10%, oxybenzone 3% 1. Sunscreens are also found in many cosmetic products including facial moisturizers, lip balms, foundations, and powders and sprays marketed for application over makeup. 2. Individual stores may carry their own brand of sunscreen. 3. Prices according to walgreens.com. Accessed July 12, 2018. 4. Meroxyl SX, patented by L'Oreal. 5. May also provide UVA2 protection. 130
absorber. Octisalate and homosalate are weak absorbers; they are generally used with other agents for additional protection. Octocrylene absorbs and is photostable; when combined with other sunscreens, it can improve the photostability of the entire product. Ecamsule is photostable and absorbs both and UVA2. 6 Inorganic The two FDA-approved inorganic (physical) sunscreens, zinc oxide and titanium dioxide, prevent, UVA1, and UVA2 penetration. Micronized (nanoparticle) formulations that improve cosmetic acceptability are now widely used; they are less visible on the skin, but may also be less effective. 7 EFFECTIVENESS In the amounts customarily applied to skin, no sunscreen product provides the labeled degree of protection. The FDA requires that the SPF be de - termined after applying 2 mg/cm 2 of the product, a very thick layer. At 2 mg/cm 2, a 4-ounce container provides only 2-4 whole body applications for an adult. Studies have shown that consumers usually apply 0.5-1.0 mg/ cm 2 or less. Applied in these amounts, sunscreens (SPF 30-100) provide an actual SPF that is about 25% of the labeled SPF. 8 Nevertheless, studies have found that long-term daily sunscreen use combined with other sun-protective measures can reduce the risk of nonmelanoma skin cancer and can reduce other adverse effects of UV exposure such as photoaging. 9-11 Prevention of Melanoma Fair skin, use of tanning beds, and a history of sunburn are associated with increased melanoma risk. 4 In a recently published population-based, case-control study in 603 Australian adults 18-39 years old with a first primary cutaneous melanoma diagnosis and 1088 controls 18-44 years old, regular sunscreen use was associated with a reduced risk of cutaneous melanoma. 12 In a prospective trial, 1621 Australians 25-75 years old were randomized to use an SPF 16 sunscreen either daily or in a discretionary manner (generally 0-2 times weekly) for 4 years. Compared with discretionary users, daily sunscreen users had half as many new primary melanomas (11 vs 22) and a 73% reduction in invasive melanomas (3 vs 11) 14 years after randomization. 13 SAFETY All organic sunscreens, especially oxybenzone, can cause contact allergic and photoallergic reactions, but these reactions are uncommon. 14 Estrogen-like activity has been reported in vitro and in some animal studies. These agents can penetrate the epidermis and small amounts can be absorbed systemically; detectable levels have been reported in human plasma, urine, breast milk, amniotic fluid, and fetal and cord blood. 15-17 Whether such exposure could result in hormonal alterations or other adverse effects in humans is unclear. 18,19 An Australian government review of the safety of titanium dioxide and zinc oxide nanoparticles concluded that these microfine particles do not penetrate or minimally penetrate the stratum corneum and underlying layers of skin, suggesting that systemic absorption and toxicity are unlikely. 20 Environmental Safety In Hawaii, legislation was recently passed banning the sale of sunscreens that contain oxybenzone and/or octinoxate because they can cause coral bleaching. 21 Detectable concentrations of sunscreens have been observed in some fish species and adverse reproductive effects have been reported. 22 USE IN INFANTS AND CHILDREN Sunscreen use is generally recommended for children >6 months old during any sun exposure that might burn unprotected skin. Inorganic sunscreens are less likely than organic sunscreens to cause irritation and sensitization. 23 VITAMIN D AND SUNSCREENS Most people require only 2-8 minutes of unprotected exposure to summer sun to maximize synthesis of vitamin D 3. Whether sunscreen use could lead to vitamin D 3 deficiency is unclear. APPLICATION For maximum efficacy, sunscreen should be applied about 15-30 minutes before sun exposure and reapplied at least every two hours and after swimming or sweating. Water-resistant sunscreens remain effective for 40 or 80 minutes while swimming or sweating; no sunscreens are waterproof. For maximum effect, approximately one teaspoon of sunscreen should be applied to the face and neck and one to each arm; two teaspoons should be applied to the torso and two to each leg. 24 When using both a sunscreen and an insect repellent, the sunscreen should be applied first. Applying the insect repellent N,N-diethyl-m-tolumide (DEET) after sunscreen has been shown to reduce the SPF of the sunscreen, but applying sunscreen second may increase absorption of DEET. The CDC does not recommend use of products that combine a sunscreen with an insect repellent because the sunscreen may need to be reapplied more often and in greater amounts than the repellent. 25 131
PROTECTIVE CLOTHING Clothing can block UV exposure. Factors that affect the level of UV protection from clothing include fabric color, fabric type, and tightness of the weave. The ultraviolet protection factor (UPF) is a measure of how effective a fabric is at blocking UV radiation; a rating of 15-24 indicates good protection, 25-39 very good protection, and 40-50 excellent protection. Washing clothes with RIT Sun Guard can confer a UPF of 30. CONCLUSION Routine application of adequate amounts of a broad-spectrum sunscreen with an SPF 15 protects against sunburn, photoaging, nonmelanoma skin cancer, and probably melanoma as well. Whether systemic absorption of small amounts of sunscreen ingredients could be harmful remains to be determined, but currently available data suggest that the benefits far outweigh the risks. 1. U Panich et al. Ultraviolet radiation-induced skin aging: the role of DNA damage and oxidative stress in epidermal stem cell damage mediated skin aging. Stem Cells Int 2016; 2016:7370642. 2. M Arnold et al. Global burden of cutaneous melanoma attributable to ultraviolet radiation in 2012. Int J Cancer 2018 April 16 (epub). 3. Questions and answers: FDA announces new requirements for over-the-counter (OTC) sunscreen products marketed in the U.S. June 23, 2011. Available at: www.fda.gov/drugs/ resourcesforyou/consumers/buyingusingmedicinesafely/ understandingover-the-countermedicines/ucm258468.htm. Accessed August 2, 2018. 4. US Preventive Services Task Force. Behavorial counseling to prevent skin cancer: US Preventive Services Task Force recommendation statement. JAMA 2018; 319:1134. 5. AAD statement on the safety of sunscreen. American Academy of Dermatology. October 22, 2015. Available at: www.aad.org/ media/news-releases/aad-statement-on-the-safety-of-sunscreen. Accessed August 2, 2018. 6. A new sunscreen agent. Med Lett Drugs Ther 2007; 49:41. 7. JB Mancuso et al. Sunscreens: an update. Am J Clin Dermatol 2017; 18:643. 8. H Ou-Yang et al. High-SPF sunscreens (SPF 70) may provide ultraviolet protection above minimal recommended levels by adequately compensating for lower sunscreen user application amounts. J Am Acad Dermatol 2012; 67:1220. 9. JC van der Pols et al. Prolonged prevention of squamous cell carcinoma of the skin by regular sunscreen use. Cancer Epidemiol Biomarkers Prev 2006; 15:2546. 10. C Ulrich et al. Prevention of non-melanoma skin cancer in organ transplant patients by regular use of a sunscreen: a 24 month, prospective, case-control study. Br J Dermatol 2009; 161 (suppl 3:78. 11. MC Hughes et al. Sunscreen and prevention of skin aging: a randomized trial. Ann Intern Med 2013; 158:781. 12. CG Watts et al. Sunscreen use and melanoma risk among young Australian adults. JAMA Dermatol 2018 July 18 (epub). 13. AC Green et al. Reduced melanoma after regular sunscreen use: randomized trial follow-up. J Clin Oncol 2011; 29:257. 14. AR Heurung et al. Adverse reactions to sunscreen agents: epidemiology, responsible irritants and allergans, clinical characteristics, and management. Dermatitis 2014; 25:289. 15. NR Janjua et al. Systemic absorption of the sunscreens benzophenone-3, octyl-methoxycinnamate, and 3-(4-methylbenzylidene) camphor after whole-body topical application and reproductive hormone levels in humans. J Invest Dermatol 2004; 123:57. 16. GM Buck Louis et al. Urinary concentrations of benzophenonetype ultraviolet radiation filters and couples fecundity. Am J Epidemiol 2014; 180:1168. 17. H Krause et al. Presence of benzophenones commonly used as UV filters and absorbers in paired maternal and fetal samples. Environ Int 2018; 110:51. 18. SQ Wang et al. Safety of oxybenzone: putting numbers into perspective. Arch Dermatol 2011; 147:865. 19. JA Ruszkiewicz et al. Neurotoxic effect of active ingredients in sunscreen products, a contemporary review. Toxicol Rep 2017; 4:245. 20. Australian Government Department of Health. Therapeutic Goods Administration. Literature review on the safety of titanium dioxide and zinc oxide nanoparticles in sunscreens. January 11, 2017. Available at: www.tga.gov.au/node/4309. Accessed August 2, 2018. 21. CA Downs et al. Toxicopathological effects of the sunscreen UV filter, oxybenzone (benzophenone-3) on coral planulae and cultured primary cells and its environmental contamination in Hawaii and the U.S. Virgin Islands. Arch Environ Contam Toxicol 2016; 70:265. 22. SL Schneider and HW Lim. Review of environmental effects of oxybenzone and other sunscreen active ingredients. J Am Acad Dermatol 2018 June 28 (epub). 23. AS Paller et al. New insights about infant and toddler skin: implications for sun protection. Pediatrics 2011; 128:92. 24. P Isedeh et al. Teaspoon rule revisited: proper amount of sunscreen application. Photodermatol Photoimmunol Photomed 2013; 29:55. 25. Insect repellents. Med Lett Drugs Ther 2016; 58:83. 132
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