seasons in the sun; A little UV exposure is inevitable.

Byline: Julia Chaplin

Out in Montauk, where I spend each July and August, my friends tease that they can spot me down the beach from the birdlike silhouette of the giant straw hat that's become my summer trademark. And when I'm back in Manhattan, people seem skeptical when I tell them I'm a surfer because of how untan my fair skin appears. ("It's the strong sunblock!" I assure them.) By all accounts, I am much more responsible than practically everyone I know about protecting myself from UVA/UVB exposure, but lately I've begun to notice tiny creases on my chest, small broken capillaries around my nose, and a few brown spots on my hands. Can anyone be that cautious, short of living in the dark? Is there any way for a surfer like me-or even an urbanite ducking in and out of shops on the weekend-to really be safe from skin cancer and photoaging? And is there some sort of checklist we should be ticking off after a summer outside or a midwinter jaunt to the Caribbean to stop abnormal cells and mottled skin from ever forming?

On a mission, I schedule a full-body exam with dermatologist Bruce Katz, M.D., director of the JUVA Medispa in Manhattan. As Katz searches for actinic keratoses (rough, precancerous red patches) and irregular moles, I nervously ramble on about my misspent-albeit exciting-youth: sunblock-free summers on the shores of Cape Cod and winters boating in Key West and the Bahamas. Tack on the spring-break sunburns in Bermuda during the boarding school years, and then learning to surf in my mid-20s, followed by a decade maxing out my sun allotment on safaris to Oahu, Baja California, and Puerto Rico, and I'm really getting scared. But, I tell Katz in earnest, now I always use eight-hour waterproof sunblocks. To which he gravely answers, "They're lying." No block is truly waterproof. Plus, he says, "it has to be applied every 40 minutes, and you have to use about one-fifth of the tube per day" to get the SPF level on the label.

Just because I'm in my mid-30s and don't look like a shriveled-up, brown-spotted raisin (yet), I'm by no means home free, Katz warns. Even the best sunscreens-those with ingredients like Mexoryl SX (Lancome, Anthelios) and stabilized avobenzone (Neutrogena, Aveeno)-don't cover the entire spectrum of skin-ruining UV rays, and sun damage, which accounts for 80 percent of the skin's premature aging, can take years to materialize. "If you got a lot of sun last summer, it may not show for ten years," he says. "Or if you get a sunburn now, a batch of brown spots might show up within three months." A mole that develops into a melanoma tomorrow could be the result of time spent outside years-even decades-ago.

Katz takes a ballpoint pen and circles a small mole (tucked in a blind spot on the lower side of my back) that looks "suspicious." He shows it to me using a small mirror and recommends a biopsy. Then he leads me over to the Visia scan, a computerized, Barbarella-like machine that photographs my face under natural and ultraviolet light and compares the image with those of thousands of other women in the database my age with similar skin types. (Visia detects surface and subsurface photo damage, but not precancers.) I place in the seventy-third percentile, with 100 being a perfect, ...