What Does SPF Mean

Shedding light on what sunscreen labels mean

Heading outdoors to enjoy some fun in the sun — at the beach, poolside or maybe in the park? You’ve probably packed a few essentials like a hat, sunglasses and beach umbrella.

There’s one more thing you should never forget — sunscreen. Whether it comes in a bottle, tube or spray can, proper sun protection is vital to help you avoid a sunburn.

“Getting a sunburn, even a minor one, damages your skin and increases the risk of premature aging and skin cancer,” says Jennifer Brooks, MD, a Geisinger dermatologist. “The best way to protect yourself from the sun’s harmful rays is to wear sunscreen.”

The sun produces two types of rays — ultraviolet A (UVA) and ultraviolet B (UVB). UVB rays are the primary cause of sunburn and skin cancer. While UVA rays also contribute to skin cancer, they lead to deeper skin damage over time like wrinkles and age spots.

SPF explained: What does SPF stand for anyway?

SPF stands for sun protection factor. All sunscreen includes an SPF rating, which refers to how well it protects against the UVB rays that cause skin to burn.

SPF measures about how long it would take your skin to burn with sunscreen when used correctly versus wearing nothing at all. For example, if it would take your bare skin 10 minutes to burn, SPF 15 should increase that by 15 times. That means it will prevent sunburn for up to 150 minutes.

The higher the number, the better the protection. An SPF 15 blocks about 93% of UVB rays, while SPF 30 blocks about 97% and SPF 50 blocks around 98%. However, nothing will give you 100% protection, no matter how high the SPF.

What sunscreen should I use?

Not all sunscreen is created equal. To find the best sunscreen for you and your family, start with the label. Look for products that say:

Broad-spectrum protection: All sunscreen protects against UVB rays. But not all sunscreen protects against UVA rays. Broad-spectrum (also called multi-spectrum or UVA/UVB) protection means it guards against both types.

Water-resistant: If you plan to be in the water or tend to sweat a lot, look for water-resistant sunblock. Note, though, that water-resistant doesn’t mean waterproof. “If you’re going swimming, reapply when you get out of the water,” says Dr. Brooks.

SPF 30: The Skin Cancer Foundation and American Academy of Dermatology recommend sunscreen with an SPF of at least 30 for optimal protection. Higher SPFs do offer slightly more protection, but the difference becomes marginal above SPF 50.

“SPF 30 is fine for the average person, as long as the proper amount is applied,” says Dr. Brooks. “Many people apply less than the recommended amount of sunscreen, so using SPF 50 or higher can be beneficial. Not using enough sunscreen can reduce its effectiveness.”

How to properly apply sunscreen

The key to maximum protection from harmful UV rays? Using sunscreen correctly.

Apply sunscreen generously to all exposed skin, including your face, ears, lips, neck and tops of feet. A general guideline is to use about a 1-ounce dollop (about the size of a golf ball) for your entire body. If you’re using a spray-on variety, spray each body part for about 5 seconds. And don’t forget to reapply every 2 hours or immediately after swimming or sweating.

“You should apply sunscreen at least 15 minutes before going outdoors,” advises Dr. Brooks. “This allows the sunscreen to properly absorb and form a protective barrier on your skin.”

Other sun safety tips

Sunscreen alone can’t fully protect your skin from the sun’s UV rays, especially if you’re outside for extended periods. So, before you head outside, here are a few other sun safety tips to shield your skin from sun damage and dodge a sunburn.

Avoid peak hours. The sun’s rays are strongest between 10 a.m. and 4 p.m., so plan outdoor activities around these peak times. If you must be outside then, stay in the shade as much as possible.
Cover up. Wear protective clothing that completely covers your arms and legs. Look for clothes with a high ultraviolet protection factor (UPF) rating, if possible. Also, add a wide-brimmed hat and sunglasses with UV protection.
Remember the sensitive spots. Don’t forget to apply sunscreen to your ears, scalp, neck and tops of your feet, and use lip balm with sunscreen — these sensitive areas can burn, too.
Don’t forget about sunscreen once summer is over. Use sunscreen all year — not just in the summer months. “UV rays reflect off sand, snow and water. It’s important to use sunscreen year-round,” says Dr. Brooks.

(And on the topic of keeping safe in the sun, stay hydrated. While it won’t stave off a sunburn, drinking enough fluids helps you avoid heat exhaustion or heat stroke.)

Regardless of brand, scent or application type, keep sunblock top of mind. “Which sunscreen to use is a personal choice,” says Dr. Brooks. “The most important thing is to use one.”