5 Sunscreen myths that could damage your skin

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PHOENIX -- Even though summer as a season hasn't officially started yet, according to the calendar anyway, it is the time of year when many people, especially kids, are spending more and more time outside.

We all understand that it is essential to protect our skin, but do you really know how to do it properly?

You might be surprised. Some of the things you think you know about sunscreen are wrong -- and potentially dangerous.

Dr. Clayton Polowy, an oncologist at Banner Desert Medical Center, ran down the five most common myths about sunscreen and skin protection for Kaley O'Kelley.

1. It's fine to use last year's bottle.

The ingredients in sunscreen break down and lose their effectiveness over time. In addition, if you're applying sunscreen appropriately, you shouldn't have any left at the end of the season.

2. Sunscreen is enough.

Whenever possible seek out shade. Also light, long-sleeved clothes are a good idea.

3. A little dab is plenty.

You should actually be using about 1 ounce for your whole body. That's one application. Polowy said most people use a dab the size of a dime. That's nowhere near enough.

"It's how you use the sunscreen, not necessarily the brand of the SPF," he explained. You have to be liberal."

The doctor suggests using a quarter-size amount each for the chest, the back, the arms and the legs. Don't forget the tops of your ears, your eyelids, your nose and your lips.

It's recommended that you reapply every two hours, especially if you're sweating or in the swimming pool.

"It's better to reapply the sunscreen on dry skin," Polowy said.

4. Waterproof works.

"Waterproof is something that's sort of a misnomer," the doctor explained. "It lasts 40 to 45 minutes in the water. If you're using waterproof sunscreen, you have to remember to reapply. Don't get the false sense of security ...."

It's also important to remember that the sun's harmful rays can bounce off the water, creating even more exposure to the skin.

"Burning can happen frequently in the water," Polowy said.

5. SPF 30 is twice as good as SPF 15.

"SPF 30 does not deliver twice the amount of protection that SPF 15 does," Polowy said. "It's more about how you're using it than the actual number. ... As you increase SPF, it doesn't necessarily increase the amount of protection."

SPF 15 protects you from 96 percent to 97 percent of the sun's harmful UV rays. SPF 30 only increases that by 1 percent to 2 percent.

In other words, save your money. SPF 30 and higher can be really expensive so it's better to use SPF 15 properly than to spring for the higher SPF.