• Mayo Clinic Minute: 3 things you might not know about sunscreen

Most people know that slathering on the sunscreen before heading outside decreases your risk of sun damage and skin cancer. Dr. Dawn Davis, a Mayo Clinic dermatologist, says there are three other things many people don't know about sunscreen.

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"No 1: Expiration dates on sunscreen bottles are legitimate. It's just like looking for produce at the grocery store. Always try to find the produce that looks the best and has the farthest away expiration date," says Dr. Davis.

No. 2: Don't expose your sunscreen to extreme heat or cold.

"Because if sunscreen gets overheated or it freezes, the chemicals are inactivated and no longer effective," says Dr. Davis.

No. 3: There is no such thing as a safe base tan. If you get a base tan simply to go on vacation, what you're doing is essentially pre-emptively giving yourself damage before — instead of damage later.

Dr. Davis adds that you should use sunscreen with a minimum of sun protection factor (SPF) of 15 every day. If you're outside, use a minimum of SPF 30.