Sunscreens are a poor second choice, but they're better than nothing, said the Swiss dermatologists who did the study.
The findings take on added urgency for residents of the northern hemisphere, where summer is approaching with its promise of long, lazy days spent at the beach or other outdoor play spots.
"Wearing sun-protective clothes and a hat and reducing sun exposure to a minimum should be preferred to sunscreens," Dr. Stephan Lautenschlager, of the Outpatient Clinic of Dermatology at Triemli Hospital in Zurich, wrote in the May 3 online edition of The Lancet.
But, this advice is felt to be "unacceptable in our global, outdoor society and sunscreens could become the predominant mode of sun protection for various societal reasons, for example healthiness of a tan, relaxation in the sun," the study authors added. "Nevertheless, sunscreens should not be abused in an attempt to increase time in the sun to a maximum."
One expert agrees with the recommendation.
"I am a proponent of the approach advocated by the [American] Cancer Society," said Dr. Martin Weinstock, a professor of dermatology at Brown University and chairman of the American Cancer Society's skin cancer advisory group. "It's called Slip-Slop-Slap. Slip on a shirt, slop on sunscreen, slap on a hat. That's the way to be safe during outdoor activities."
According to Lautenschlager's group, the type of clothing you wear can make a big difference in sun protection factor (SPF). For example, tightly woven, thick garments made of denim, wool or polyester offer the best protection, while cotton, linen and acetate are much less effective, they noted.
In terms of sunscreens, there are two kinds -- inorganic and organic. Inorganic sunscreens work by scattering UV light using zinc or titanium oxides. This type of sunscreen is well tolerated by the skin and produces few allergic effects. It is recommended for children, the study authors said.
Organic sunscreens absorb the UV rays, and are made up of complex organic molecules that are "photoprotective." Organic screens should be put on 15 to 30 minutes before going out in the sun.
And waterproof or water-resistant sunscreens should be used to reduce the need for reapplication after swimming followed by toweling, friction with clothing or sand, and sweating, Lautenschlager's group noted.
Weinstock thinks that SPF factor is the most important consideration when choosing a sunscreen. "I recommend SPF 30 or greater," he said.
Lautenschlager's group warned that while studies have found that sunscreens protect against acute UV skin damage and nonmelanoma skin cancers, it's not clear whether they help protect against melanoma, the most dangerous form of skin cancer.
"The population has to be advised how to best make use of sunscreens," the authors wrote. "The application of a liberal quantity of sunscreen is, by far, the most important factor for effectiveness of the sunscreen, followed by the uniformity of application and the specific absorption spectrum of the agent used."
Dr. Doris Day, a dermatologist at Lenox Hill Hospital in New York City, offers another safety rule to minimize your exposure to UV rays.
"There is a nice rule -- called the shadow rule -- that is very useful," Day said in a statement. "The shorter your shadow, the more dangerous the rays of the sun. So, for example, at noon when the sun is highest, you have little to no shadow, and that is the best time to try to stay indoors or in the shade."
Skin cancer -- including melanoma and nonmelanoma malignancies -- is the most common of all cancers, accounting for about half of all cancers. An estimated one million cases of nonmelanoma skin cancers are diagnosed annually in the United States. Most are basal cell -- about 800,000 to 900,000. Squamous cell cancer occurs less often -- perhaps 200,000 to 300,000 cases annually. People do not often die of these cancers. About 1,000 to 2,000 people die of nonmelanoma skin cancer each year in the United States, according to the American Cancer Society.
Melanoma, on the other hand, causes most skin cancer deaths, even though it accounts for just 3 percent of all skin cancer cases. The American Cancer Society estimates there will be 59,940 new cases of melanoma in the United States this year, and about 8,110 people will die of the disease.
HealthDay News, May 3, 2006.