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Sunscreen Timing

August 24, 2010

A listener asks: how long should you wait after applying sunscreen before going outside?


Timing your sunscreen…I’m Bob Hirshon and this is Science Update.

It’s the height of summer, and listener Corinna of Oakland wants to know why she’s been told to wait up to thirty minutes after applying sunscreen before going outside. We asked clinical research Joe Stanfield of Suncare Research Labs in North Carolina. He says in order to provide maximal protection, the polymers in sunscreens need time to bind to the skin.

JOE STANFIELD (Suncare Research Labs):
You need to put the product on when the skin is dry, and then give it sufficient time to dry and establish the bond. You can just touch the skin and you can tell whether the product has dried on the skin.

He says when the sunscreen feels smooth and not tacky to the touch, you’re probably good to go. It’s best to reapply often, and avoid too much sun exposure during the middle of the day. And if you have a science question, give us a call at 1-800-why-isit. If we use your question, we’ll send you a Science Update mug! I’m Bob Hirshon, for AAAS, the science society.