COVER STORY sunburns, and skin blistering (think UV Burning ). UVB rays are associated with SPF (sun protection factor): a rating that tells us how effective particular sunscreen is against UVB rays. The strength of UVB rays fluctu-ates with the time of day with the highest risk of damage between mid-morning to mid-afternoon from Spring-Fall. Sunscreen, sunblock or suntan lotion, is a photoprotective prod-uct that has the ability to absorb or reflect a portion of the sun’s UV rays. It can come in many different formulations including lotions, sprays, tells, foams, sticks, and powder. Sunscreen can also be added to clothing such as sunglasses, sunhats, and other sun protective clothing. The use of photoprotective products dates back to at least the ancient Egyptian civiliza-tions. There is evidence that they used ingredients such as rice bran, jasmine, and lupine to pro-tect themselves from the rays of the sun. The first sunscreen was invented in Australia in 1932 by the chemist, H.A. Milton Blake. He created a UV filter called ‘salol, or phenyl salicylate, at a 10% concentration. There are two main types of sunscreens available on the mar-ket today: inorganic and organic sunscreen. Both forms work by absorbing UV light and convert-ing it to heat. Inorganic sunscreen, which is often mistakenly referred to as ‘physical sunscreen’, is made up of minerals/ionic compounds such as zinc oxide or titanium dioxide. Inorganic sunscreen was originally thought to work by scattering and reflecting UV rays. Newer studies found that inor-ganic sunscreens may absorb up to 95% of UV light, deflecting only about 5% Organic (chemical) sunscreens consist of molecules with a car-bon-chain structure. They work by absorbing UV light, convert-ing them to heat, and then releas-ing them from the body. While there are many chemical sun-screen filters in the European/ Asian market, only 17 are ap-proved in Canada. These include homosalate, Mexoryl SX, Mexo-ryl XL, and avobenzone. INORGANIC SUNSCREEN PROS Less irritating to sensitive skin Micronized minerals may have less white cast compared to non-mi-cronized minerals Microfine zinc oxide is more protective against UVA + UVB than microfine titanium dioxide Zinc oxide protects against UVA and UVB (290-400 nm) Titanium dioxide protects against UVA and UVB (290-340 nm) CONS Thicker consistency which may lead to breakouts Visible white cast, which may not be ideal for individuals with deeper skin tones ORGANIC (CHEMICAL) SUNSCREENS PROS Allow for more UVA protection (protects against UVA1 which has a longer wavelength) May be beneficial to individuals who are prone to hyperpigmentation and aging Have less/no white cast compared to physical sunscreens CONS Active components may be absorbed into the body; this does not mean that it is necessarily harmful May be irritating to individuals Tends to be greasier in texture May contain benzene Recently, an independent laboratory called Valisure LLC found that 78 out of 249 batches of sunscreens and after-sun products from 69 brands had detectable levels of benzene, a known carcinogen. This is, however, a contamination issue, not a sunscreen issue. When applying sunscreen, it is important to remember the number 2: two finger-lengths worth of sunscreen applied on the face and neck every 2 hours. In order to achieve the SPF (sun protection factor) provided by the sunscreen, you need to use approximately 2mg/cm2 of sunscreen on the face and neck, the arms, the torso, and the legs. This works out to be about 1 tsp or the length of your index and middle finger. RESOURCES: American Academy of Dermatology Association. Skin Cancer Types: Melanoma Signs and Symptoms. www. aad.org Accessed March 20, 2022. Azoury SC, Lange JR (October 2014). “Epidemiology, risk factors, prevention, and early detection of melanoma”. The Surgical Clinics of North America. 94 (5): 945–62, vii. Canadian Cancer Society. Melanoma skin cancer statistics. www.cancer.ca. Accessed March 20, 2022 Cole, Curtis et al. “Metal oxide sunscreens protect skin by absorption, not by reflection or scattering.” Photodermatology, photoimmunology & photomedicine vol. 32,1 (2016): 5-10. doi:10.1111/ phpp.12214 Edlich, Richard F et al. “Photoprotection by sunscreens with topical antioxidants and systemic antioxidants to reduce sun exposure.” Journal of long-term effects of medical implants vol. 14,4 (2004): 317-40. Kanavy HE, Gerstenblith MR (December 2011). “Ultraviolet radiation and melanoma”. Seminars in Cutaneous Medicine and Surgery. 30 (4): 222–8. Matta, Murali K et al. “Effect of Sunscreen Application on Plasma Concentration of Sunscreen Active Ingredients: A Randomized Clinical Trial.” JAMA vol. 323,3 (2020): 256-267. doi:10.1001/ jama.2019.20747 Nadim S (2005). “Sunscreen Evolution”. In Shaath N (ed.). Sunscreens : regulations and commercial development (3 ed.). Boca Raton, Fl.: Taylor & Francis. Norval M, Wulf HC (October 2009). “Does chronic sunscreen use reduce vitamin D production to insufficient levels?”. The British Journal of Dermatology. 161 (4): 732–6. Rigel, Darrell S.; Weiss, Robert A.; Lim, Henry W.; Dover, Jeffrey S. (January 30, 2004). Photoaging. CRC Press. Sander, et al. The efficacy and safety of sunscreen use for the prevention of skin cancer. CMJA 2020; 1802-1808. Skin Cancer Foundation. www.skincancer.org Accessed March 20, 2022. World Cancer Report 2014. World Health Organization. 2014. pp. Chapter 5.14. 10 Chiropractic and Naturopathic Doctor July/August 2022 www.Cndoctor.ca Photo: © shaitan1985 / Adobe Stock
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