Deb Balzer | (TNS) Mayo Clinic News Network

Did you know sunscreen has a shelf life and can expire? Or that too much heat or cold can ruin a new bottle?

Protecting your skin from harmful sun rays will help against inflammation, burns, premature aging and, most importantly, skin cancer.

Dr. Dawn Davis, a Mayo Clinic dermatologist, has more on sunscreen shelf life and other facts to help make decisions as you head into the sun.

You might think a dermatologist is going to ask you to ban the sun.

“There’s nothing wrong with being outside in the sun,” says Dr. Davis.

UV, or ultraviolet light, is a carcinogen. That’s where sunscreen helps.

“Sunscreen can act as a carcinogen barrier to help keep your skin safe,” says Dr. Davis.

Keep these sunscreen facts in mind when you’re reaching for your favorite bottle:

— Sunscreen can expire, affecting the active ingredient and the preservative.

— Sunscreen is sensitive to extreme temperatures. Keep it out of direct sun, and don’t let it freeze during winter storage.

— People of color need to wear sunscreen.

Bottom line, everyone over age 6 months needs sunscreen — babies included.

“It is a layman’s myth that children do not get skin cancer. And it’s a layman’s myth that a person of color cannot have skin cancer,” Dr. Davis says.

And lastly, Dr. Davis says, “There literally is no such thing as a waterproof sunscreen.”

Apply sunscreen, and after you get wet, reapply.

To be effective, sunscreen needs to be used liberally so be generous with your portions.

It’s recommended to use 1 ounce (30 milliliters) of sunscreen — the amount in a shot glass — to cover exposed parts of the body. You might need to apply more, depending on your body size. If you have a 4-ounce (118-milliliter) bottle, you’ll use about a quarter of it during one application.

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