Sun Block Sunscreen And More - Protecting Your Skin: Skin Health
Content provided by the Faculty of the Harvard Medical School
Sun block, sunscreen, and more
There's a difference between sun blocks and sunscreens. True to their name, sun blocks prevent the sun from reaching your skin. If you've ever been a lifeguard, you're probably familiar with the sun-blocking agent zinc oxide, the creamy white coating that has saved many a nose from too much sun. Zinc oxide and its chemical cousin, titanium dioxide, are sun blocks because they reflect ultraviolet radiation away from the skin surface. Both are available in skin tones and fashion colors, while titanium dioxide is also available in a clear formula. These ingredients are used in some commercial lotions such as those labeled as "non-chemical" or "for sensitive skin." Sun blocks are highly effective in protecting against UVA and UVB rays (see "Don't get burned by improper sunscreen use").
Don't get burned by improper sunscreen useIt's simple, right? Use a sunscreen, and you won't get a sunburn. Wrong. Every summer, throngs of beachgoers head out with their SPF 15, 30, or 45 in tow, but still manage to get burned. In interviews with 67 adult sun worshippers at a popular beach in Galveston, Texas, researchers from the University of Texas Medical Branch in Galveston reported that 73% of those who used sunscreen became sunburned. The problem isn't with the sunscreen, but how people apply it. Most people don't apply enough, or they don't apply it frequently enough to be effective. A major problem, according to the researchers, is failure to apply more sunscreen after swimming. The American Academy of Dermatology (AAD) recommends reapplying sunscreen immediately after swimming, or every two hours if you stay out of the water. In fact, the academy says that people who wait more than two and a half hours to reapply have five times the chance of getting sunburned as those who reapply every two hours. The AAD also advises people to use about a shot glass full of sunscreen for adequate coverage of exposed areas of the body and to apply sunscreen about 15–30 minutes before going outdoors. |
Sunscreens, on the other hand, absorb rather than reflect UV radiation. In recent years, the most widely used sunscreen ingredients have included benzophenones, which protect against UVA, and cinnamates and salicylates, which protect against UVB. You'll see these ingredients listed as oxybenzone, octyl salicylate, or octyl methoxycinnamate, to name a few. A major drawback is that many of these ingredients break down after several hours when exposed to sunlight, which means that the sunscreens need to be reapplied to be effective.
But two new sunscreens — Anthelios SX and Helioplex — provide longer-lasting protection against UVA and UVB rays. Research shows that Anthelios SX, which was approved by the FDA in 2006, retains 80% of its UVA protection and 90% of its UVB protection five hours after application. The product combines a new UVA absorber called ecamsule with an older UVA absorber (avobenzone) and an older UVB absorber (octocrylene). Helioplex is a stabilized formulation of avobenzone and oxybenzone, a longstanding UVB and UVA absorber. Helioplex and Anthelios SX appear to be comparable in sun protection and stability.
When choosing a sunscreen, most people look at the product's sun protection factor (SPF) rating. The American Academy of Dermatology (AAD) recommends using sunscreen with an SPF rating of at least 15. People with fair skin or at high risk for skin cancer may want to go higher. The higher a sunscreen's SPF rating, the longer it protects against sun exposure.
But that's just part of the equation. The SPF rating only measures how well a sunscreen blocks or absorbs UVB rays. Therefore, the academy and federal public health agencies advise using a sunscreen that protects against both UVA and UVB rays. Products labeled "broad spectrum" often contain several different sun protection ingredients in order to cover the broadest possible range of UV radiation. But to what extent they do so is difficult to determine because there is no good method of measuring how well a sunscreen protects against UVA. It's an issue the FDA is grappling with in developing new sunscreen labeling regulations.
| Last updated: | July 20, 2007 |
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Medical content reviewed by the Faculty of the Harvard Medical School. Harvard Health Publications, Copyright © 2007 by President and Fellows of Harvard College. All rights reserved. Used with permission of StayWell.
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