Health Topics

Sunscreen Basics

By DuPage Medical Group Dermatology

Are you confused by all the sunscreen options and ingredients?

  • Sun Protection Factor (SPF) 30 or greater is recommended for protection of UVB rays.
  • Broad Spectrum Protection protects against both UVA and UVB rays.
  • Common active ingredients in most sunscreens include zinc oxide, titanium dioxide, mexoryl sx or avobezone (3%).

The SPF strength depends on skin sensitizing to the sun. For example, It takes 20 minutes for your unprotected skin to start turning red. Using an SPF 15 sunscreen theoretically prevents reddening 15 times longer, about 5 hours. That does not mean you have 5 hours of protection without reapplying your sunscreen.

Another way to look at it is in percentages. SPF 15 filters out approximately 93 percent of all incoming UVB rays. SPF 30 keeps out 97 percent and SPF 50 keeps out 98 percent. Regardless of strength, no sunscreen should be expected to stay effective longer than 2 hours without reapplying. Even on cloudy days.

Sunscreens should be applied 30 minutes before sun exposure to allow the product to fully bind to your skin. Reapply sunscreen every 2 hours and also immediately after swimming, toweling off or sweating. Don’t forget use extra caution near water, snow and sand as they reflect the damaging rays of the sun.

Topics and Subtopics: Skin Health

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