by Susan Y. Chon, MD

You know you need sunscreen. But with so many lotions, sprays and gels to choose from, how do you know which sunblock will actually prevent sunburns — and skin cancer?

When it comes to shielding your skin from the sun, the type of sunscreen you choose is as important as how you use it.

I hear many people blame their sunscreen when they get sunburned. But the problem usually isn’t the sunscreen. It’s that the user isn’t reading the label and applying the sunscreen properly.

Before heading outdoors, follow these tips to maximize your sunscreen’s protection.

1. Get UV-A and UV-B protection

Always opt for a sunscreen that provides both UV-A and UV-B protection. This way, you’ll protect your skin from ultraviolet-B (UV-B) rays, which cause sunburns and skin damage, as well as ultraviolet-A (UV-A) rays that increase your risk for skin cancer.

Also make sure the sunscreen you choose contains zinc oxide or titanium dioxide. These ingredients help to block both UV-A and UV-B rays.

2. Choose SPF 30 or higher

Always use a sunscreen with SPF (Sun Protection Factor) 30 or higher. The SPF in your sunscreen absorbs and reflects the sun’s rays so they don’t burn or damage your skin.

Keep in mind, though, that higher isn’t that much better when it comes to SPF numbers. Many people think they can safely stay in the sun longer if they choose a higher SPF, but that isn’t the case.

Here’s why: SPF protection doesn’t increase proportionately with the designated SPF number. So while SPF 30 absorbs 97% of the sun’s burning rays, SPF 50 absorbs just slightly more — 98%.

If you choose an SPF higher than 30, you should still treat it as though you’re using SPF 30. That means you should apply just as much sunscreen — and just as often — as you would if you were using SPF 30.

3. Apply sunscreen early — and liberally

Your skin can take up to a half-hour to absorb sunscreen. So, plan ahead and apply sunscreen 30 minutes before going outside.

And, don’t skimp on the sunscreen. For sunscreen to do its job effectively, you should apply one ounce of sunscreen — the size of a golf ball — to every part of your body exposed to the sun. That includes your ears, feet and back of the neck.

4. Reapply sunscreen every two hours

Forget all-day protection. Sunscreen wears off after just a couple of hours. So, make sure you lather on another golf ball-sized glob every two hours.

In some cases, you should reapply sunscreen every 60 to 90 minutes. Do this if you’re:

• Using a spray sunscreen. It needs to be reapplied more often because it washes off more easily.
• Swimming or sweating. Water, snow and sand can intensify the sun’s rays and cause a greater burn.

5. Don’t rely on sunscreen alone

Unfortunately, sunscreen can’t completely prevent sunburns, blisters and skin cancer. But you can give your skin some added protection by wearing:

• lip balm with SPF 30 or higher
• a tightly woven hat with a wide brim
• wrap-around sunglasses with UV protection
• a tightly woven, dark long-sleeved shirt or special sun-protective clothing

You also can protect your skin by seeking shade from the sun from 10 a.m. to 4 p.m. That’s when the sun’s harmful UV rays are strongest.

Remember, no sunscreen provides 100% protection from the sun. But by taking these added precautions and taking the time to apply — and reapply — sunscreen properly, you can greatly curb your chances for sunburns and skin cancer.

Susan Y. Chon is assistant professor in the Department of Dermatology at The University of Texas MD Anderson Cancer Center.

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