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  1. Excessive sunlight exposure can cause health problems such as skin cancer, premature skin ageing, cataracts and immune system suppression.[1] This happens as sunlight, known to contain harmful UV rays, induces the formation of free radicals in the skin. The application of sun protection creams, or sunscreens, reduces these free radicals, suggesting their role as antioxidants.[2] While not free from side effects, the US Food and Drug Administration stated that the benefits from the use of sunscreen outweigh the risks.[3] It is well known that sunlight induces the generation of vitamin D in human skin (which is known for multiple positive health effects), and recent studies have discovered that the application of sunscreens doesn’t block the synthesis of this crucial vitamin.[4] Sunscreen creams can be either chemical or physical. Chemical sunscreens absorb sunlight and transform the UV rays into much safer light or heat energies. Physical sunscreens, on the other hand, scatter or reflect sunlight.[2] Depending on their composition, sunscreen products can also present both features to maximise their efficacy.[5] Some creams may contain preservatives, alcohol or fragrances and, as recommended by the US Environmental Protection Agency (EPA), should be avoided by people with skin allergies.[6] “Sun protection factor” (SPF) is a measurement used to describe how effective a sunscreen is in protecting against sunlight.[7] The value represents a ratio between the amount of sunlight needed to cause sunburn in people who use the sunscreen as compared to those without. A higher value does represent better protection, but the protective effect does not increase in a linear fashion. For instance, SPF 15 protects against 93.3% of UVB rays, while SPF 30 protects against 96.7% of UVB rays, and SPF 45 protects against 97.8% of UVB rays.[8] It is also important to note that SPF is related to the intensity of the sunlight exposure rather than its duration.[9] Therefore, time of the day, geographical factors and weather are all important elements that need to be considered before deciding what sunscreen should be used. Various chemicals in sunscreen products have been associated with adverse effects. Para-aminobenzoic acid, despite banned in today’s manufacturing practice, might still be found in older-made products, and can cause severe allergic rashes, acne and blisters.[7][10] A skin condition called “photoallergic contact dermatitis” can develop due to the use of octocrylene, benzophenone-3 (oxybenzone) and butyl methoxydibenzoylmethane.[11] Laboratory studies also showed that benzophenone-3 might affect endocrine function,[12] but its concentration in sunscreen products is too low for a chemical to cause significant negative effects on health.[2] Certain chemical constituents found in sunscreens, such as benzophenone-3  and dioxybenzone, can also react with the chlorine found in swimming pools, reducing their efficacy and causing the chemicals to harm the skin.[13] Physical blockers in older sunscreens, such as zinc oxide, may block skin pores and cause acne. Newer sunscreens are made with nanoparticle physical blockers, so zinc oxide is hardly ever used today,[2] but the issue with nanoparticles is that their toxicity risk has not been yet determined. Do sunscreens protect you from melanoma? EPA claims they do not,[5] and staying in the shade is the best protection. Some studies report increased rates of melanoma (a type of skin cancer) due to sunscreen use,[14] but this occurs as a result of more frequent sunbathing activities rather than being caused by the sunscreens themselves.[15] A comprehensive review carried out in 2003 analyzed articles from 1966 to 2003 about sunscreen and melanoma risk and found no such association.[16] It can thus be confirmed that overexposure to sunlight may increase the risk for melanoma, with or without sunscreens. The FDA states that applying 2mg/cm2 of sunscreen works best. Some studies have shown that many consumers apply insufficient amounts of sunscreen, with values ranging from 0.39 to 1.0 mg/cm2.[17] Sunscreens should be reapplied every two hours or when the sunscreen gets wiped or washed off the body.[2] Powdered and spray-on sunscreens should be avoided, as the micro-particulates contained in them might be inhaled, which can be hazardous. As for babies, getting away from the sun is the best protection. Since babies have higher surface-area to body-weight ratio, along with their less mature skin, their risk of getting the side effects from sunscreen use is higher.[18] Sunscreen use benefits clearly outweigh the dangers. However, we should always keep in mind that sunscreen application should not be a reason to stay longer in the sun; rather, it is a tool at our disposal to lower the risks from hazardous sunlight exposure. Despite scientific advances in the formulation of sunscreens, the best protection from the sun is to stay in the shade. It is also important to note that, according to the most recent studies, sunscreens do not help to prevent melanoma. Application of sunscreens on young children should also be limited, since they are more exposed to the side effects caused by toxic ingredients.  [1] Health Effects of UV Radiation | Sun Safety | US EPA. (2017). Epa.gov. Retrieved 8 April 2017, from https://www.epa.gov/sunsafety/health-effects-uv-radiation [2] Latha, M. S., Martis, J., Shobha, V., Sham Shinde, R., Bangera, S., Krishnankutty, B., … Naveen Kumar, B. R. (2013). Sunscreening Agents: A Review. The Journal of Clinical and Aesthetic Dermatology, 6(1), 16–26. [3] Understanding Over-the-Counter Medicines. (2017). Fda.gov. Retrieved 8 April 2017, from https://www.fda.gov/Drugs/ResourcesForYou/Consumers/BuyingUsingMedicineSafely/UnderstandingOver-the-CounterMedicines/default.htm  [4] Kannan, S., & Lim, H. (2014). Photoprotection and vitamin D: a review. Photodermatology, Photoimmunology & Photomedicine, 30(2-3), 137-145. http://dx.doi.org/10.1111/phpp.12096  [5] Lademann, J., Schanzer, S., Jacobi, U., Schaefer, H., Pflücker, F., & Driller, H. et al. (2005). Synergy effects between organic and inorganic UV filters in sunscreens. Journal Of Biomedical Optics, 10(1), 014008. http://dx.doi.org/10.1117/1.1854112  [6] Sunscreen: The Burning Facts. (2006) (1st ed.). Retrieved from https://www.epa.gov/sites/production/files/documents/sunscreen.pdf  [7] CDC - Sun Safety - Skin Cancer. (2017). Cdc.gov. Retrieved 8 April 2017, from https://www.cdc.gov/cancer/skin/basic_info/sun-safety.htm  [8] Dale Wilson, Brummitte, Summer Moon, and Frank Armstrong. “Comprehensive Review of Ultraviolet Radiation and the Current Status on Sunscreens.” The Journal of Clinical and Aesthetic Dermatology 5.9 (2012): 18–23. Print. [9] Sun Protection Factor (SPF). (2017). Fda.gov. Retrieved 8 April 2017, from https://www.fda.gov/aboutfda/centersoffices/officeofmedicalproductsandtobacco/cder/ucm106351.htm [10] Nash, J., & Tanner, P. (2014). Relevance of UV filter/sunscreen product photostability to human safety. Photodermatology, Photoimmunology & Photomedicine, 30(2-3), 88-95. http://dx.doi.org/10.1111/phpp.12113 [11] A European multicentre photopatch test study. (2012). British Journal Of Dermatology, 166(5), 1002-1009. http://dx.doi.org/10.1111/j.1365-2133.2012.10857.x [12] Kim, S., & Choi, K. (2014). Occurrences, toxicities, and ecological risks of benzophenone-3, a common component of organic sunscreen products: A mini-review. Environment International, 70, 143-157. http://dx.doi.org/10.1016/j.envint.2014.05.015 [13] Sherwood, V., Kennedy, S., Zhang, H., Purser, G., & Sheaff, R. (2012). Altered UV absorbance and cytotoxicity of chlorinated sunscreen agents. Cutaneous And Ocular Toxicology, 31(4), 273-279. http://dx.doi.org/10.3109/15569527.2011.647181 [14] Bastuji-Garin, S., & Diepgen, T. (2002). Cutaneous malignant melanoma, sun exposure, and sunscreen use: epidemiological evidence. British Journal Of Dermatology, 146(s61), 24-30. http://dx.doi.org/10.1046/j.1365-2133.146.s61.9.x [15] Westerdahl, J., Ingvar, C., Måsbäck, A., & Olsson, H. (2000). Sunscreen use and malignant melanoma. International Journal Of Cancer, 87(1), 145-150. http://dx.doi.org/10.1002/1097-0215(20000701)87:1<145::aid-ijc22>3.0.co;2-3 [16] Dennis, L. (2003). Sunscreen Use and the Risk for Melanoma: A Quantitative Review. Annals Of Internal Medicine, 139(12), 966. http://dx.doi.org/10.7326/0003-4819-139-12-200312160-00006 [17] Petersen, B., & Wulf, H. (2014). Application of sunscreen − theory and reality. Photodermatology, Photoimmunology & Photomedicine, 30(2-3), 96-101. http://dx.doi.org/10.1111/phpp.12099 [18] Should You Put Sunscreen on Infants? Not Usually. (2017). Fda.gov. Retrieved 10 April 2017, from https://www.fda.gov/ForConsumers/ConsumerUpdates/ucm309136.htm