Look for sunscreen labeled ‘broad spectrum’
DEAR DOCTOR: I want to be better about protecting my skin from the sun. Are all sunscreens the same, and are they equally effective?
DEAR READER: Ultraviolet radiation (also referred to as UV rays) from the sun is the No. 1 cause of skin cancer. Sunscreen is any cream, spray or lotion that combines specific ingredients that will prevent UV rays from reaching your skin. Two kinds of UV rays — UVA and UVB — are targeted by sunscreen.
UVB rays cause sunburn. UVA rays, which reach into the deeper layers of your skin, cause premature aging. Both types of ultraviolet rays increase your risk of a variety of skin cancers.
You’ll notice that sunscreen is rated by a number system — SPF 15, for example — which signifies its level of Sun Protection Factor. The SPF factor of a sunscreen refers to its level of protection against UVB rays only. It does not measure protection against UVA rays, which are equally harmful. To be sure you are getting protection against both UVA and UVB rays, choose a product whose label says “broad spectrum.”
What the SPF number tells you about any brand
of sunscreen is how it will protect your skin. Just multiply the amount of time it takes for your skin to begin to burn by the SPF number.
Let’s say you typically start to turn pink after 10 minutes in the sun. A sunscreen with an SPF factor of 15 will, in theory, give you 150 minutes of protection. However, numerous factors are at play. Did you go swimming? Are you sweating? Did you put on enough sunscreen? Did it rub off on your hands or clothes? The rule of thumb put forth by skin cancer specialists is that an application of sunscreen lasts no longer than two hours. And if any swimming or sweating or rubbing occurred, reapply liberally and often.
The Food and Drug Administration, which regulates sunscreen products in the United States, recommends that you use an SPF of at least 15. But the experts at the American Academy of Dermatology say an SPF of at least 30 is the safest bet.
Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health.
Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA 90095.