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The ABCs and SPFs of sunscreen

June 22, 2015 | UCI Health

Summer or winter, sunscreen is a necessary fact of life for Southern California residents. But purchasing a sun-protection product can be a complicated process if you don’t know what to look for.

“There’s an epidemic of skin cancer in the United States,” says Dr. Kristen Kelly, UCI Health dermatologist.

“The two most powerful defenses against this type of cancer are protective clothing and sunscreen. But many people don’t understand how to read a sunscreen label and what’s necessary in a sun-protection product for optimal protection.”

What SPF means

SPF, written on every sunscreen bottle, stands for sun protection factor, and has a number. This figure, which can range from 2 to 50+, indicates how much more sun protection an average person would attain from using the product. For example, if you select a sunscreen with an SFP of 15, you’ll be protected 15 times more than if you hadn’t used it.

“Contrary to popular belief, an SPF of 30 isn’t twice as effective as a sunscreen with an SPF of 15,” says Kelly.

“An SPF 15 sunscreen filters 93 percent of the sun’s UVB rays, while a product with an SPF of 30 shields against 97 percent. Higher SPFs offer smaller increments of skin protection.” Currently, the highest SPF is 50+ and there are no products available that filter 100 percent of the sun’s rays.

The American Academy of Dermatology recommends an SPF rating of at least 30. However, the SPF number indicates only the product’s ability to protect against UVB rays — the kind that damages the skin’s superficial layers. UVA rays, on the other hand, penetrate the skin more deeply.

Both can cause skin cancer and premature skin aging.

The broad-spectrum question

To ward off both types of ultraviolet radiation, you should select a product that’s labeled “broad spectrum.” This means you’ll be protected against both UVA and UVB rays. Unlike SPF numbers for UVB rays, there’s currently no FDA-approved rating system that measures UVA protection levels.

Kelly adds: Make sure to read the entire sunscreen label, front and back. It’s loaded with important information.

”Make sure to check whether any product you’re considering has a ‘skin cancer/skin aging alert’ in the drug facts section of the label,” advises Kelly.

Sunscreen products that aren’t broad spectrum or are broad spectrum with an SPF rating from 2 to 14 will be labeled with a warning that the product has been shown to reduce sunburn — but not cancer or early aging. In this case, it’s time to put the product back on the shelf and search for better sun protection, she says.

Water-resistant sunscreen

Another important feature to look for in sunscreens is what’s called “water resistance.” Until 2012, sunscreen manufacturers were free to make exaggerated claims about their products, describing them as “waterproof” and “sweatproof.” Then the FDA reined them in.

Now, even broad-spectrum sunscreen with an SPF over 15 can’t be labeled “waterproof” or “sweatproof” because no sun-protection product stays on the body when exposed over time to water or perspiration. Nor can a product be called a "sunblock," because no sunscreen is capable of completely blocking the sun's rays.

When shopping for a sunscreen, look for the words “water resistant” and the specific amount of time you can rely on the product’s declared SPF protection to keep you sun-safe when swimming or sweating. The FDA permits only one of two water-resistance times on labels: 40 minutes or 80 minutes. After that, you need to reapply your sunscreen.

How to apply sunscreen

No matter how effective a sunscreen is shown to be in testing, it won’t work if you don’t apply it correctly. Kelly recommends at least one ounce — or an average shot glass — of sunscreen to adequately cover your entire face and body, applied at least 20 minutes before going outdoors. 

“Typically, people use about one-third to one-half the amount of sunscreen used by the lab to determine an SPF number for a product,” says Kelly.

Skimping on sunscreen can have serious consequences: If you apply only one-quarter of the recommended amount of an SPF 30 sunscreen, the SPF rating is actually reduced to 2.3, according to the Environmental Working Group, a nonprofit advocacy organization for human and environmental health.

And don’t forget the problem areas that are often skipped in a sun-protection routine:

  • Ears, lips (use a lip balm with SPF protection), scalp and back of neck
  • Armpits
  • Tops of feet, backs of hands and the backs of knees
  • Areas under swimsuit edges and bathing suit straps

By adding sunglasses that block 100 percent of UV rays, you can protect your eyes from cataract-causing UV radiation.

In addition to sunscreen, you should follow the tried-and-true recommendations of sun safety:

  • Wear a broad-brimmed hat
  • Stay out of the sun between 10 a.m. and 3 p.m.
  • Seek shade when possible
  • Wear a long-sleeved shirt, long pants and other clothes that offer sun protection

“Sunscreen isn’t just for light-skinned people,” reminds Kelly. Some darker-skinned individuals don’t believe they can get skin cancer. But this isn’t the case: Ultraviolet rays may lead to skin cancer in anyone. “Sunscreen and protective clothing are important for everyone, no matter what their color or ethnicity,” says Kelly.

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