Screening sunscreens: Which is the best for you?

During summer trips to the beach, we dab ourselves with sunscreen, often with very high sun protection factor (SPF) number, and then go out and have fun, assuming that we’re out of harm’s way. To some extent, we are. Sunscreens make sense, along with limiting sun exposure and wearing protective clothing.

But many of us may be getting a false sense of security – thinking that these sunscreens give complete protection against skin cancer risk or premature skin aging. The truth is, many sunscreens – even those with high SPF ratings – don’t stop the entire spectrum of the sun’s ultraviolet light. Some contain ingredients that might do the job, but there is no standard test, like the SPF rating, to confirm it.

Because of these concerns, the US Food and Drug Administration (FDA), which regulates sunscreens as over-the-counter drugs, has postponed issuing final regulations until December of this year. But this doesn’t mean that choosing from among umpteen types of sunscreen is impossible. It’s quite simple, if you follow a few recommendations – and accept some uncertainties.

A Refresher On Uv Radiation

Sunscreen is designed to block, absorb, or reflect the invisible part of sunlight. This energy is carried to earth in the wavelengths of ultraviolet radiation (UVR). The shortest of these, ultraviolet C (UVC), is absorbed by the earth’s atmosphere long before it can reach the skin. Intermediate-wavelength ultraviolet B (UVB) carries the energy that causes sunburn. It is also the major factor in basal cell carcinoma and probably in squamous cell carcinoma, the two most common types of skin cancer.

Long-wavelength ultraviolet A (UVA) is 1,000 times less effective in producing sunburn than UVB, but is more plentiful and penetrates more deeply into the skin. UVA used to be considered relatively harmless, but researchers now believe it’s as important as UVB in causing skin cancer, including melanoma, the rarest but most serious form of the disease. UVA also speeds skin aging by damaging collagen, the fibrous protein found in skin and other tissues.

SPF RATING

Sunscreen makers are required to identify the SPF ratings of their products. The SPF rating is based on a calculation comparing how long a small patch of skin takes to redden with and without sunscreen. If skin reddens in 10 minutes without sunscreen, it will redden in 150 minutes when protected by an SPF-15 sunscreen and in 300 minutes with an SPF-30 sunscreen. In essence, SPF measures how much UVB is getting to the skin.

Sunscreens sold today range from SPF-2 to SPF-50, although most brands have a rating of at least 15. The FDA has proposed that products with an SPF rating of more than 30 simply be labeled as SPF-30+. That is partly because a very high SPF number gives people a false sense of security: They don’t burn, so there is nothing warning them to get out of the sun. The results of a European study in the August 4, 1999 issue of the Journal of the National Cancer Institute illustrate this problem. The study compared the sunbathing habits of young French and Swiss participants randomized to use either an SPF-30 or an SPF-10 sunscreen. During a 20-day vacation, the SPF-30 group spent 14 hours more in the sun than their counterparts with SPF-10 sunscreen.

The FDA has another argument for an SPF 30+ label: As the SPF number gets higher, the differences in protection get smaller and smaller. So, for example, the difference in the amount of sunlight kept off the skin between an SPF-30 and an SPF-50 sunscreen is just 1.3 percent.

The standard advice is to gets a sunscreen with an SPF rating of at least 15. People who have fair skin, many freckles or moles, a family history of skin cancer, skin that burns easily, or a prescription drug that makes their skin light-sensitive should go for an SPF-30. But keep in mind that SPF is based on the use of a set amount of sunscreen – 2 milligrams per square centimeter of skin. That works out to a bit more than an ounce for a 5-foot-8-inch person per application. Most people use a half to a quarter of that amount, however, and at those levels, an SPF-15 sunscreen has an SPF of just 3-7. Consider this: To get the full SPF value out of sunscreen, a family of four should be using an entire 4-ounce bottle during a day at the beach – even more if they are spending a lot of time in water.

‘BROAD-SPECTRUM’ PROTECTION

Any sunscreen with an ingredient that absorbs or blocks UVA can be billed as offering "broad-spectrum" or "UVA-radiation protection." But the FDA and the sunscreen makers haven’t agreed upon a standard test or rating scale for UVA protection – something that would be comparable to SPF. High-SPF sunscreens do protect skin against part of the UVA spectrum – the shorter wavelengths that are closest to UVB – but they don’t usually provide any protection against longer UVA wavelengths.

Research suggests that few sunscreens fully deliver on their broad-spectrum claims. A study published in the December 2000 issue of the Journal of the American Academy of Dermatology evaluated 59 sunscreens offering UVA protection. Most (93 percent) did shield against the UVA wavelengths nearest to UVB, but only 10 percent protected against the longer UVA wavelengths. The most effective products contained titanium dioxide, zinc oxide, or avobenzone. A smaller 1999 study reported similar results. Of the 11 products analyzed, six promised UVA protection. And those six varied greatly in how much of the UVA spectrum they held at bay.

The upshot of this research is that when you shop for a broad-spectrum sunscreen, it is probably best to look for one that contains zinc oxide, titanium dioxide, or avobenzone. But even these three ingredients have drawbacks. Some studies suggest that avobenzone might degrade when exposed to UVA, the very thing it is supposed to protect against. Zinc oxide and titanium dioxide are white and can make a sunscreen milky. Now, many of these sunscreens are finely ground, or "microfine," zinc oxide or titanium dioxide so they are clear. Which is better – zinc oxide or titanium dioxide? No one really knows, although one recently published study found that zinc oxide was less visible and more protective than titanium dioxide.

WATER RESISTANCE

Water-resistant and waterproof sunscreens are big sellers. To qualify as water resistant, a sunscreen must maintain its SPF rating after 40 minutes in the water. The standard waterproof label is 80 minutes. The FDA has proposed replacing waterproof with "very water resistant" because it believes waterproof – like the term "sunblock" and "all-day protection" – misleads consumers.

WHAT YOU SHOULD DO

It is going to take some trial and error on your part but find a brand that you like wearing and doesn’t bother your skin: Sunscreen in the bottle never protected anybody from anything. Enough people react to an ingredient called PABA to create a significant market for PABA-free formulas. People with rosacea might want to steer clear of padimate-O because it is irritating, although a recent Mount Sinai Hospital study found that the addition of dimethicone and cyclomethicone offsets the problem. Both of these ingredients are common in PABA-free sunscreens. Zinc oxide and titanium dioxide are not absorbed by the skin and are rarely irritating.

Don’t go by just SPF. Look for a broad-spectrum brand. The UVA protection might not be 100 percent, but it is better than nothing. You also need to make sure that the broad-spectrum sunscreen contains ingredients that are proven UVA protectors – zinc oxide, titanium dioxide, or avobenzone. And there are enough question marks about avobenzone that a preference for zinc oxide or titanium dioxide is warranted. There is some evidence that adding vitamins C and E to sunscreens might make them more effective, but more research needs to be done to prove it.

The sun is like any other exposure: Some people are genetically fortunate and their bodies, in this case the skin, can handle the peril without a problem while others are exquisitely sensitive. In general, fair-skinned people are far more vulnerable. Still, sunlight is a carcinogen, and getting too much of it is something we all need to be wary of.