Rules for a Safe Summer

By now we all know that the sun can kill: About 1 million new skin cancers are diagnosed each year in the United States, and about half of all new cancers are skin cancers, according to the American Academy of Dermatology. And thanks to increased awareness about skin cancer, we also know the summer mantra: Wear sunscreen, wear sunscreen, wear sunscreen. What we may not know, however, is how to choose and use sunscreen properly, so we can maximize our protection each time we apply it and step out into the sun. Here, rules to follow for a safe summer:

Sun protection factor (SPF) has to do with the amount of time a product protects the skin from the reddening caused by ultraviolet rays, compared to how long it would take without the product. If you would normally burn in 20 minutes, a sunscreen with an SPF of 15 will protect you for 15 times longer, or about five hours.

"Fifteen is probably sufficient for most people most of the time," says Dr. Neil S. Goldberg, a dermatologist who practices in the New York communities of Bronxville and White Plains. "But if somebody has had skin cancer... or burns very easily, they should probably use an SPF of 25 or higher." Goldberg says that anything less than 15 is probably worthless, whether you are sun-sensitive or not.

Past an SPF of 15, the incremental sun-protective benefit diminishes. An SPF of 15 blocks out 93 percent of harmful rays; an SPF of 25 about 96 percent; and an SPF of 30 about 97 percent.

Even if you're not a particularly sun-sensitive person, it may be worthwhile to choose an SPF higher than 15. The level of protection indicated on a product is only reached if the correct amount of sunscreen is used (1 ounce per use is considered optimal). However, most people apply too little, and while it's best to try to use the recommended amount, if you use a higher number SPF, you will get greater protection using less product.

While SPF is a universal measure of protection against UVB rays, known to cause sunburns and many forms of skin cancer, there is currently no standard for UVA rays, which are less potent but more prevalent. UVA rays are thought to play a role in the wrinkling and aging of skin, and may contribute to skin cancer. Some sunscreens now offer what is called "broad-spectrum" protection, or protection against both UVA and UVB rays.

Avobenzone (Parsol 1789) chemically absorbs UVA rays. Some question exists as to whether it becomes less protective when exposed to sunlight. Results of studies to determine this should be available in the next year or two. For now, Dr. Henry W. Lim, chairman of the department of dermatology at the Henry Ford Health System in Detroit, calls avobenzone "the best UVA protection on the market in the U.S."

Zinc oxide and titanium dioxide offer another form of UVA protection by physically deflecting the rays. It's the same thick white stuff lifeguards used to use, but now it's available in a microfine, almost-clear form. Lim says that it doesn't absorb as well as avobenzone or some other products, but it does offer significant protection. It is thought to be safer for small children and people who have allergic reactions to many sunscreens.

The ingredients above are most helpful when combined with high-SPF products that also block out UVB rays.

In the next year or two Lim says Mexoryl, an ingredient currently used in Europe that offers both UVA and UVB protection, should be available in the United States.

There is currently no standard for when products need to be reapplied, but reapplying is key to sun safety, especially when you are away from home. "When somebody goes to the beach for the day, they go for the day, not just for 80 minutes," which is the amount of time a water-resistant product is tested to stay on in the water, says Dr. Martin Weinstock, professor of dermatology at Brown University and chairman of the Skincare Advisory Group of the American Cancer Society.

A good rule of thumb is to put sunscreen on every two hours and every time you get out of the water (reapply every 80 minutes if your product is labeled "water resistant"). Depending on your activity -- if you're sweating, for example -- you may need to reapply more often. The same rules apply if the product you're using is a moisturizer with sunscreen as an added ingredient.