The intensity of the UV rays a person will encounter -- and the subsequent crimson consequences -- depends on lots of factors like season, latitude, altitude, time of day, cloud cover and skin type. Plus, while trudging behind a lawnmower can give you a rosy pink glow, a day at the beach can leave you more on par with the unfortunate lobsters served up in oceanside surf and turf joints. That's because sand and water (along with concrete, snow and other surfaces) reflect sunlight back up, meaning it hits you coming and going.
To make matters worse, even if you started out with a good coating of sunscreen, if your time at the beach lasted longer than two hours and not a second was spent reapplying sunscreen, the chances of a bad burn typically shoot right through the roof. If your fun included activities like frolicking among the ocean waves or sprinting back and forth across a sandy volleyball court, things get even worse. Those sunburned scientists didn't give up, however, and continued to develop innovative new formulas for more advanced sunscreen products.
Different sunscreens achieve different levels of water resistance through a variety of means. In addition to ingredients that deal with UV waves like titanium dioxide, zinc oxide and oxybenzone, they also have ingredients that can endure an onslaught of water and sweat. For example, these agents may form an adhesive film that's particularly good at sticking to skin and staying in place. Sunscreens that have proven they're able to arm wrestle with water and sweat are generally labeled like this:
- Water-resistant: The product can handle up to 40 minutes of exposure to water (or sweat) and still be effective.
- Very water-resistant: The product can handle up to 80 minutes of exposure to water (or sweat) and still be effective.
If you do find a sunscreen labeled "water-proof" or "sweat-proof," however, don't believe the hype -- as we learned on the last page that's just not possible. Sometimes the term water-proof is used in place of very water-resistant, so be sure you know what to expect. Plus, even ones that are resistant should be reapplied after someone sweats or gets wet, just to be on the safe side. You can't be too careful when it comes to protecting your skin; the threat of cancer is very real.
For more information about everything under the sun, visit the links below.
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- Aust, Duncan. "Sunscreen Composition with Enhanced SPF and Water Resistant Properties." Free Patents Online. Feb. 13, 2007. (Dec. 21, 2009) http://www.freepatentsonline.com/7175834.pdf
- Boyles, Salynn. "FDA Wrapping Up Sunscreen Label Changes." WebMD. May 21, 2009. (Dec. 21, 2009) http://www.webmd.com/skin-problems-and-treatments/news/20090521/fda-wrapping-up-sunscreen-label-changes
- FDA's Tanning Web site. (Dec. 21, 2009) http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/Tanning/default.htm
- Singer, Natasha. "Do Sunscreens Have You Covered?" New York Times. July 5, 2007. (Dec. 21, 2009) http://www.nytimes.com/2007/07/05/fashion/05skin.html
- "Sunblock." University of California, San Francisco. May 4, 2007. (Dec. 21, 2009) http://www.dermatology.ucsf.edu/skincancer/General/prevention/Sunscreen.aspx
- "Sun Protection and Sunscreen." University of Iowa. (Dec. 21, 2009) http://www.uihealthcare.com/topics/skinhealth/sunprotection.html
- "Sun Protection Products." The Cosmetic, Toiletry and Perfumery Association. (Dec. 21, 2009) http://www.thefactsabout.co.uk/Content.asp?menuid=33&submenuid=94&pageid=94&menuname=How+do+sunscreens+work%3F&menu=sub
- "Sunscreen: Answers to Your Burning Questions." Mayo Clinic. March 27, 2009. (Dec. 21, 2009) http://www.mayoclinic.com/health/sunscreen/SN00044
- "Sunscreen." WebMD. October 2008. (Dec. 21, 2009) http://www.webmd.com/drugs/drug-366-sunscreen+top.aspx
- "Sunscreens Explained." The Skin Cancer Foundation. (Dec. 21, 2009) http://www.skincancer.org/Sunscreens-Explained.html
- "Sunscreens/Sunblocks." American Academy of Dermatology. (Dec. 21, 2009) http://www.aad.org/public/publications/pamphlets/sun_sunscreens.html
- The Sun Safety Alliance Web site. (Dec. 21, 2009) http://www.sunsafetyalliance.org/index.html
- "What's the Difference Between a water proof and a water resistant sunscreen?" PharmacyMix.com. (Dec. 21, 2009) https://www.pharmacymix.com/water-proof-vs-water-resistant-sunscreens.htm
- Williams, D. F. and Schmitt, W. H. "Chemistry and technology of the cosmetics and toiletries industry." Chapman and Hall. 1996. (Dec. 21, 2009) http://books.google.com/books?id=q1W7VtF8rJgC&lpg=PA137&ots=_aJ05q1sdL&dq=sunscreen%20chemistry%20waterproof&pg=PA137#v=onepage&q=&f=false