Sunscreen
March 25, 2015
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Sunscreen by Jonathan Schreiber, MD, PhD

Finally, it is time to dust off the Roleez, grab the surf board, find those boogie-boards, and see if the old beach chairs will still open up. While sorting through your beach tote, you may run across old bottles of sunscreen.  Are they still good?  There should be a date on the bottle, listed as a month and a year.  If you can’t find the date, can’t read the date, or if the product in the bottle has separated into a distinct liquid and solid layer, or has become discolored, it is time to toss the bottle.

Even if you find some sunscreen that appears intact, this is the time to stock up for the summer.  Sunscreen has been shown to decrease the risk of skin cancer, and slow the photo-aging process, which contributes to unwanted wrinkles and dark spots.

Look for a sunscreen that has an SPF of 30 or higher.  The SPF, or sun protection factor, is a multiplier that compares the time it takes to develop a sunburn with the product compared to without the product.  Therefore, with an SPF of 30 applied properly, it would take 300 minutes to develop a sunburn with the sunscreen compared to 10 minutes without it.

Why do we need so much protection?  People rarely apply the amount of sunscreen required to achieve the labeled SPF.  When sunscreens are tested, a standard thickness is used; however, in real world applications, people rarely use enough to achieve even half the thickness used in the testing laboratories.  In fact, you would need to use 1oz or one fourth of a standard bottle to achieve the rating on the bottle.  That is why physicians changed their recommendation of an SPF of 15 to an SPF of 30.  Using a higher SPF provides reasonable protection, even when the product is applied in a thinner film than is used in laboratory testing conditions.

Look for a sunscreen that says “broad spectrum,” or UVA and UVB protection.  UVB causes sunburns.  Older sunscreens only protected people from UVB.  We now know that UVA can contribute to sun damage and aging skin.  Agents that block UVA are zinc oxide, titanium dioxide and parsol 1789, also known as avobenzone.  Be sure your sunscreen contains at least one of these agents to protect you from UVA.  There are other UVA blockers that are currently available in other countries, and may eventually make their way to the United States.

Remember, you can still get a suntan, and even a sunburn while using sunscreen.  Be sure to apply sunscreen before you go out, and then every two hours while out in the sun.  It is a good idea to reapply sunscreen after spending time in the water, even if the sunscreen is labeled water resistant.  Protective clothing, such as rash guards and hats, as well as umbrellas and canopies will also help you to safely extend your time outdoors.

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