Picking the right sunscreen

By John Bonifield
CNN Medical Producer

It’s Memorial Day Weekend—the unofficial start of summer! I’m hitting the beach and taking plenty of sunscreen with me.

Many of you will be spending hours in the sun in the months ahead. Sadly this year, more than a million of you will also learn that you have skin cancer.

We all know sun blocks can work to prevent burns and disease, but how do you pick the right one?

The American Academy of Dermatology recommends using a broad-spectrum sunscreen. When we talk about sun damage, we’re actually talking about damage to the skin that’s caused by ultraviolet light: UVB and UVA rays.

UVB rays lead to sunburns. When you buy sun block that provides SPF protection, you’re protecting yourself against UVB rays. SPF indicates the level of protection.

UVA rays penetrate deep into the middle layer of your skin. They can lead to wrinkles and age spots. They can also diminish your body’s ability to protect against cancer by weakening the immune system.

Both UVB and UVA rays can cause skin cancer, but not all sun blocks protect against UVA rays. For broad-spectrum protection, you want to buy one that does.

Now, a lot of people wonder about strength: SPF 85 sounds like a lot more protection than SPF 30 or SPF 15, but the difference between them actually starts to get pretty small.

For example, an SPF 15 sun block lets in about 6 percent of the sun’s UVB rays. An SPF 30 lets in only about 3 percentof those rays. An SPF 85 lets in a little more than 1 percent.

So, you’re going to get only slightly more protection with the higher SPFs, but that doesn’t mean you should let yourself bake in the sun longer. The recommended minimum is an SPF 15.

Whatever SPF you pick, be sure to slather on enough sunscreen—a shot glass-full is about right, the recommended one ounce. Reapply frequently, especially after swimming or if you've been sweating profusely.

On “House Call with Dr. Sanjay Gupta” this weekend, we’re kicking off a three-part series called “Saving Your Skin.” We’ll tell you more about picking the right sunscreen.

Also, let us know: what are your skin concerns this summer?

Editor's Note: Medical news is a popular but sensitive subject rooted in science. We receive many comments on this blog each day; not all are posted. Our hope is that much will be learned from the sharing of useful information and personal experiences based on the medical and health topics of the blog. We encourage you to focus your comments on those medical and health topics and we appreciate your input. Thank you for your participation.