Stanford Medicine Newsletter Updates For the Local Community


How to weather summer's health challenges

Playing it safe in the sun

Susan Swetter, MD, a professor of dermatology, warns that sun exposure can lead to DNA damage to the skin cells that accumulates over time.


Brooks Bahr, MD, a clinical assistant professor of dermatology at Stanford, has paid the price for his carelessness under the sun. The fair-skinned Bahr has played outdoor sports his entire life, including football at the University of Utah. By the time he was 32, he had developed a basal cell skin cancer, which was removed.

“Growing up, I always played in the sun and only wore sunscreen occasionally. It caught up with me,” Bahr said. “Now I wear sunscreen every day and encourage everyone else to do the same.”

Summer brings more intense sunshine and with it the need to pay special attention to the skin, especially among children and teens. Research shows that periods of severe sun exposure or sunburn—especially during childhood—increases the chances of developing skin cancer.

“When you get sporadic but intense ultraviolet radiation exposure, it causes an insult to skin cells’ DNA, which is believed to initiate the malignant changes that can lead to skin cancer, including melanoma,” said Susan Swetter, MD, a professor of dermatology at Stanford and director of the Stanford Pigmented Lesion and Melanoma Program. “Once those DNA mutations occur, your cells are more susceptible to damage from ultraviolet light. This damage accumulates over your lifetime.”

Ultraviolet (UV) radiation from the sun and artificial sources (i.e., tanning beds) is responsible for sunburn, accelerated aging of the skin (called photoaging) and skin cancer. Approximately 95 percent of UV radiation is composed of UVA-type rays, which are strong all day and all year long. The other 5 percent are UVB rays, which penetrate the skin less deeply but are 400 times more intense in the summer and at midday between 10 am and 4 pm. UVB rays play a key role in sunburn and skin cancer.

Brooks Bahr


Sun protection during outdoor activities is mostly a matter of common sense: avoid the hottest hours of the day, seek shade when possible, use sunscreen liberally and wear protective clothing like hats, long sleeves and sunglasses—and practice these habits consistently.

Broad-spectrum sunscreens that block both UVA and UVB rays are recommended for daily use on the face, neck, hands and any other areas not covered by clothing. A recent study in Australia showed that people who used sunscreen regularly were at lower risk of melanoma, the most deadly form of skin cancer, compared to those who used it only occasionally. But it is also important to use a sufficient amount.

“Most  people use less than half of the sunscreen they need to achieve the actual SPF level of the product,” Swetter said.

She suggests using a sunscreen with SPF of at least 30, applying two to three tablespoons to the body and one tablespoon to the face. Reapply sunscreen every two to four hours while in the sun, and more often when swimming or sweating, as there is no such thing as a waterproof sunscreen. Sunlight reflected off the water or beach also increases UV exposure.

Tanning-bed trouble

Swetter strongly advises against the use of indoor tanning beds, which emit UVA and UVB radiation at up to 15 times the intensity of natural sunlight.

“The tanning-bed industry has long promoted the concept that tanning beds give a safe and healthy tan because they don’t allow as much of a burn,” Swetter said. “But that’s a complete fallacy. Any time tanning occurs, there is cellular damage to the skin. There is no safe tan apart from sunless tanners, which simply stain the top layer of the skin.”

The U.S. Food and Drug Administration considers artificial UV radiation from tanning beds a dangerous carcinogen, and the American Academy of Dermatology warns that people who use them increase their risk of developing melanoma by 75 percent.

One in five Americans will develop skin cancer in his or her lifetime, the vast majority of which will be basal cell and squamous cell carcinomas. Melanoma accounts for only 4 percent of cases but more than 80 percent of all skin cancer deaths. People with fair skin and those with a number of moles, sun sensitivity or a family history of skin cancer are more likely to develop melanoma. Older men have the highest incidence and mortality rates from melanoma, but the number of new cases in young women is on the rise—likely due to tanning-bed use.

Athletes at risk

Exercise is certainly part of a healthy lifestyle, but outdoor exercise requires sun protection. Research has shown that perspiration increases the skin’s susceptibility to sun damage and could increase skin cancer rates in athletes and outdoor enthusiasts.

Bahr, Swetter and other Stanford dermatologists initiated a program to educate the university’s student athletes about their increased risk and help them improve their sun safety habits. Called SUNSPORT (Stanford University Network for Sun Protection, Outreach, Research and Teamwork), the program is a collaboration of the Stanford dermatology and athletic departments, the Stanford Cancer Institute and Stanford Hospital & Clinics.

SUNSPORT dermatologists provide skin screenings, give educational talks and materials to athletes and coaches, and work closely with the trainers who interact with the teams throughout the year.

“The rates of skin cancer in the coaches and significant sun damage we’ve seen in 18-to 22-year-olds are striking,” Swetter said. “Our hope is that through improved sun protection practices, we can prevent skin cancer in what we now consider a ‘higher risk’ population.”

SUNSPORT aims to leverage the popularity of Stanford Athletics to help spread the sun safety message to students, faculty and fans. “Having Stanford athletes serve as ambassadors to their peers and to younger school-age athletes is also a major goal,” Swetter said.

“We formed SUNSPORT to help Stanford’s outdoor athletes and their fans realize the dangers of sun exposure without adequate protection,” added Bahr. “I learned from my own experience that the danger is real, but it can be avoided.”

Learn more about SUNSPORT at

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