(The following was filed for a Business Week story in June 1991.)

Sun Screen Usage Tips

By Bob Andelman

You're at the beach. The cooler is full of cold drinks and a picnic lunch. You're wearing a new bathing suit that shows a little more skin than last year's model. And while you want to get a little color from the sun, you know too much is dangerous. Out comes the sun screen. Spread it around; maybe a friend can help with those hard to reach spots. There - you're safe.

Or are you?

What's the SPF? Do you know one SPF from another? Is your sun screen waterproof? What does "apply liberally" really mean? Did you re-apply protection after toweling off? Or do you assume that "waterproof" meant all day, come what may? And does your sun screen protect you from both UVB and UVA rays?

Let's start with SPF. It stands for "sun protection factor" and is the number found prominently displayed on sun screen packages. A lower number means less protection, a higher number means more. SPF 15 is right for most people. If you normal acquire a sunburn in 30 minutes, a product with SPF 15 gives you 15 times 30 minutes (7.5 hours) to get the same amount of sun on your skin. But lotions, gels, sprays and creams need to be applied more accurately than people think to provide the advertised level of protection. A thin veneer will not be enough; an ounce is the recommended amount to be spread around. And a sun screen that is labeled "waterproof" means a little more than "lite" does in foods.

"Those claims are usually pretty good," says Dr. Richard Taylor, a professor of dermatology at the University of Miami, Fl. and chief of dermatology at the Miami Veterans Administration Hospital. "But that doesn't mean you can go in the water with impunity. You should probably reapply lotion."

Some say a higher SPF - 30 to 50 - can indicate a greater degree of waterproofing, but this is not an industry standard or FDA-approved measure. And being waterproof does not mean the product will stay on the skin indefinitely. If extended stays in the water and natural perspiration don't reduce a waterproof sun screen, then drying yourself with a towel will certainly rub it off.

Most sun screens protect against UVB rays. But new research shows that UVA rays are also harmful and stopping them is not as simple as reaching for higher SPFs. Zinc oxide blocks UVA, as do Burroughs Wellcome's "Filteray" and Herbert Laboratories' "Photoplex."

The ingredients that make up most sun screen products are essentially the same basic constituents whether the final form is an oil or a cream. "Sometimes you get poundcake," says an independent cosmetics industry consultant. "Sometimes you get French pastries." That may explain vast differences in price for essentially the same result. There are aesthetic differences, ranging from a liquidy, alcohol-based application to a moisturizing cream. Men like a different feel on their skin than women do. And fragrances range from medicinal and herbal to watermelon and coconut.

"What I tell patients is to go out and buy one that is SPF 15 or less," says Taylor. "As far as I'm concerned, anything over SPF 15 is just marketing. You can't get over 15 times sun exposure in a normal day." Taylor says higher SPFs expose users to more chemicals than can possibly do them any good.

Suzanne Grayson disagrees with the doctor on that point. "It's like chicken soup - it's not going to hurt," says the Santa Barbara-based cosmetics marketing consultant. "An SPF 40 is used by people who have sensitive skin, who burn easily, or who may be in the sun longer. They're putting more on so it will last longer," she insists. The FDA has not endorsed SPFs over 15.

A new twist in the marketing of sun screen is the development of waterproof products aimed at young children who go in and out of water more often than their parents. "This is the age of segmentation," says Avon's David Lawson, brand manager for personal care and sun care products. Lawson acknowledges that the ingredients and formulations are often identical to those for adults, which are less expensive. "If I try to put everything into one product, a lot of consumers wouldn't believe it," he says. Taylor doesn't think it's a bad tactic. "It's hard to get angry with that. They're doing a good thing" by encouraging protection for kids, he says.

Attitudes toward using sun screens are evolving - slowly.

"We used to equate a sun tan with good health," says Allan Mottus, publisher of the health care industry newsletter "The Informationist." "They used to say, 'Look at that tan, that man looks good.' Now, it's, 'Good lord, look what that woman is doing to herself!'"