Sunscreen has a shelf life and other facts to know

By Deb Balzer

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. 

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

Watch this Mayo Clinic Minute video:

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.

Sunscreen application tips

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.

Learn more

Learn more about skin cancer and find a clinical trial at Mayo Clinic.

Join the Skin Health Support Group on Mayo Clinic Connect, an online community moderated by Mayo Clinic for patients and caregivers.

Also, read these articles:

• Common types of skin cancer
• Removing skin cancer with Mohs surgery
• Who should be screened for skin cancer?
• Melanoma in darker skin tones: Race and sex play a role, Mayo study finds

A version of this article was originally published on the Mayo Clinic News Network.