Insights from the Editor

Tis the season for sunscreen - and for lots of advice in the media about how to use it properly. Among the often-repeated tips: Choose a product with an SPF of at least 15 that protects against both UVA and UVB rays; apply liberally to all exposed areas; and reapply every two hours.

That's good advice, but there's more to the story. Here are five facts about sunscreen that often go unreported:

Sunscreen has not been proven to protect against all forms of skin cancer.
While sunscreen has been shown to guard against squamous cell skin cancer, a less dangerous form of the disease, it has never been proven to protect against melanoma, the most deadly type. Nor is there definitive evidence that it guards against basal cell skin cancer, the most common form. It's possible that relying on sunscreen as a first line of defense, as we often do, may actually increase the risk of certain skin cancers by allowing us to spend more time in the sun and giving us a false sense of security. While sunscreen is an important tool for protecting skin against the sun's damaging rays, it's best used as a second line of defense, behind measures such as avoiding the sun, seeking shade, wearing a hat, and covering up. (Watch this to learn more about sun-protective clothing.)

Ultra-high SPF sunscreen offers very little extra protection.
Recently, manufacturers have been introducing sunscreens with SPFs as high as 85 or 100. In fact, these astronomical numbers are largely a marketing gimmick. While it may seem that SPF 90 provides three times the protection of SPF 30, the math doesn't work that way. SPF 30 blocks about 97% of UVB rays, while SPF 90 does only marginally better, blocking 99%. No sunscreen blocks 100% of rays. An SPF of 15 or 30 provides adequate protection for most people - assuming they use the sunscreen correctly.

Some products' claims about UVA protection are deceptive.
Increasingly, sunscreens claim to offer "broad spectrum" protection against both UVA and UVB rays - something that's important because both types contribute to skin cancer. But it turns out that many of these sunscreens have only limited effectiveness against UVA rays. Manufacturers are able to get away with this deception because there are no FDA regulations in place regarding UVA labeling. (After years of delay, such rules are expected to be finalized later this year.) To make sure you're getting a sunscreen that provides UVA protection, look for ingredients such as zinc oxide, titanium dioxide, avobenzone, or Mexoryl SX on the label.

There's no such thing as a 100% "waterproof" sunscreen.
Some products claim to be waterproof, implying that you can swim or sweat all day without having to worry about reapplying. While a sunscreen can be water resistant - meaning that its SPF protection remains intact after exposure to water for 40 minutes (and 80 minutes for sunscreens that are labeled "very water resistant") - no product is completely waterproof. To be safe, it's best to reapply sunscreen after you get in the water or sweat heavily. Oh, and by the way: In case you're wondering about those widely-circulated Internet rumors claiming that waterproof sunscreens cause blindness, they're false.

Products endorsed by health groups aren't necessarily better.
Some products carry seals of approval from respected health groups, implying that these sunscreens are superior to others. For example, you can find the logo of the American Cancer Society on certain Neutrogena sunscreens. It turns out, though, that only Neutrogena products are eligible for this recognition. It's part of a marketing deal between the two organizations, in which Neutrogena pays ACS for the right to use its logo. Likewise, the nonprofit Skin Cancer Foundation has a "seal of recommendation" program that it offers to qualified sunscreens and other sun protection products. But to be eligible, a manufacturer must be a member of the group's "Corporate Council." And how does one receive that honor? Contribute $10,000 to the organization. The bottom line is these stamps of approval are often more about money and marketing than solid science. They're best ignored.

Now that you're in the know, test your knowledge of sun safety with our video quiz.