Common sunscreen mistakes to avoid this summer

ARI SHAPIRO, HOST:

You've heard the advice to put on sunscreen. Ads assure you that this brand or that one is the best. Well, it seems that picking the right sunscreen is less important than using enough. That's one of several tips we hear from NPR's Allison Aubrey.

ALLISON AUBREY, BYLINE: When I rummaged through last season's pool bag and found a few bottles of half-used sunscreen, I figured I'd lather some on. I mean, at $10 a bottle, why not? But Ida Orengo, a dermatologist at Baylor College of Medicine, persuaded me to toss it out.

IDA ORENGO: I always tell people that you need to look at the expiration date and get rid of them. And even if they haven't expired, my kind of mantra is every spring, I buy all new sunscreen for my household.

AUBREY: The active ingredients can degrade. And she says bacteria can get into the creams, too. So once I tossed out the old ones, I was in the market for new sunscreens. I'd always bought the standard chemical sunscreen sprays in the past, though recent studies found some of these chemicals can get into the bloodstream. Dr. Tola Oyesanya, a dermatologist with Kaiser Permanente in the Baltimore area, told me she recommends an alternative - physical sunscreens made from titanium dioxide and zinc oxide. They're also called mineral sunscreens, and some newer versions go on without that thick, white, pasty look.

TOLA OYESANYA: I think that zinc oxide and titanium dioxide are much, much safer than chemical sunscreens. Because they're so inert, they're less likely to enter the bloodstream.

AUBREY: And they're better for sensitive skin since they're less likely to irritate, she says. As for choosing the SPF, lots of sunscreens come in SPF 50 or even 80. But it turns out the sunscreens with the highest sun protection factor aren't necessarily better.

OYESANYA: SPF 30 is sufficient, and that's because SPF 30 is going to filter 97% of the UV rays that are coming through from the sun. And as we go up in SPF - SPF 50, SPF 75, SPF 100 - you're really getting a minuscule increase.

AUBREY: She tells her patients to focus less on the SPF and more on the amount of sunscreen they use. And Dr. Orengo agrees. One mistake many people make is using too little. The recommended amount is about an ounce and a half of liquid sunscreen.

ORENGO: We always say, like, a shot glass full of sunscreen is for the whole body.

AUBREY: And about a teaspoon for the face. When it comes to spray sunscreens, Dr. Oyesanya says it's a little trickier to gauge the amount.

OYESANYA: I think that spray sunscreens are a bit risky. Because of the spray, it's easy to miss a whole area of your body, especially if you're applying it outside. The wind may carry the sunscreen away.

AUBREY: She says make sure all the parts of your body that need to be covered feel wet after you spray. And remember; you need to reapply about every two hours. Dr. Jennifer Holman, who is a fellow of the American Academy of Dermatology, says sunscreens don't last very long, especially when people sweat and swim.

JENNIFER HOLMAN: If you're exposed to the water, even with sunscreens labeled as water-resistant, you're really only getting about 80 to 90 minutes of protection.

AUBREY: So reapply often, even on cloudy days. Dermatologists say some of the worst sunburns are linked to overcast days, when people may assume they don't need sunscreen.

HOLMAN: You're still getting about 80% of the UV rays filtered through those clouds on a cloudy day. So you absolutely can still, you know, experience damage from UV radiation on a cloudy day.

AUBREY: So keep your sunscreen handy even when it's not sunny. But Dr. Oyesanya says one mistake people make is to leave sunscreen stored in the trunk or glovebox of their car, where it gets too hot.

OYESANYA: The sunscreen is actually being degraded by heat. And so the components of the sunscreen that are supposed to protect you are getting broken down slowly over time.

AUBREY: One thing you can keep in your car is clothing or hats to protect you from the sun. Baseball caps protect part of your face. But dermatologists say what's better is a three-inch-brim hat made with tightly woven material. Dr. Jennifer Holman says fair-skinned people are at higher risk of burns and melanoma. But people with dark skin are vulnerable to damage from the sun, too.

HOLMAN: I mean, I've cut skin cancers off of every skin type that I can think of because that risk is still there.

AUBREY: That's why sunscreen is recommended for people of all ages and skin types. Allison Aubrey, NPR News.

(SOUNDBITE OF JONAS BROTHERS SONG, "SUMMER BABY") Transcript provided by NPR, Copyright NPR.