• Ultraviolet B (UVB) rays are the primary cause of sunburn and skin cancer, although ultraviolet A (UVA) rays also play a role in skin cancer development. UVA radiation also leads to premature signs of aging in the skin, called photo-aging. They penetrate more deeply into the skin than UVB. They can also pass through the ozone layer and glass. Both types of UV radiation penetrate through clouds.
How to protect your skin
• Apply sunscreen with an SPF (sun protection factor) of at least 15 to 30 daily before going outside.
• Use enough: Two tablespoons, a palm-full, for full body coverage and one teaspoon for the face and ears. Reapply at least every two to three hours, especially if you're sweating or swimming. If your scalp is not covered fully by hair, try a spray-on sunscreen or a sunscreen gel.
• Wear a hat that covers your face, ears and the back of your neck.
• Cover as much of your skin as you can. A tightly woven, light-colored fabric can protect skin better than inadequately applied sunscreen.
• Avoid the mid-day sun (between 10 a.m. - 4 p.m.), especially in the summer, unless you are fully protected. Seek shade when possible.
• Wear sunglasses to protect your eyes.
• Avoid tanning beds. The type of light they emit causes both non-melanoma skin cancers and melanoma.
What to know about sunscreens
• Use an SPF of at least 30, but be aware that this number only reflects how well UVB rays are filtered. Measuring a sunscreen’s protection against UVA rays is more complicated but now required for coverage of both types of UV radiation.
• Look for sunscreens labeled broad spectrum, meaning their ingredients provide protection against the full range of UVA and UVB. Sunscreens with an SPF beyond 50 do not appear to offer significantly increased UVB protection. New FDA guidelines will limit all American sunscreens to SPF 50+.
• No sunscreens are fully waterproof, although they may be labeled as water resistant.
• Sunscreens do have expiration dates and will deteriorate if stored at higher temperatures.
• Depending on their ingredients, sunscreens either absorb or reflect harmful rays. Sunscreens with micronized titanium dioxide or zinc oxide, in conjunction with chemicals like avobenzone and oxybenzone, combine the two approaches.
Dermatologists from Stanford Hospital & Clinics will provide free skin examinations from 8 a.m. to noon, Saturday, June 2 in the Dermatology Clinic on the fourth floor of Pavilion B at the Stanford Medicine Outpatient Center, 450 Broadway, Redwood City. The screening is recommended for people with fair skin, excessive exposure to the sun, many or atypical moles or a parent or sibling who has had skin cancer. For more information, call 650-723-6316 For more information about skin cancer care at Stanford, visit stanfordhospital/melanoma or call 650-498-6000.