Sunscreen. Sun block. Suntan lotion. What exactly is SPF? How much is enough? What is the FDA doing about it?
Now that we've (finally) got some sunshine in Seattle, it's time for a talk about sunscreen. Sunscreen is formed of organic and inorganic particles that are designed to block and/or absorb ultraviolet (UV) light from ths sun. Physical sunscreens reflect light, Chemical sunscreens absorb light. Many products have both forms inside. Blocking sunlight also blocks vitamin D creation, an issue that many patients have concerns about.
The SPF number reflects how well a sunscreen protects against UVB light, the type of UV ray that causes squamous cell carcinoma and basal cell carcinoma. It does not measure protection against UVA rays which cause melanoma or infrared light which also affects sun damage levels. UVB causes the most common types of skin cancer, but UVA causes the most deadly. SPF is, unfortunately, very inaccurate because most people don't put on enough. Also, wiping it off, swimming, and sweating all minimize its effectiveness, regardless of whether it is labeled "sweatproof" or "waterproof". Plus, we're supposed to be reapplying it every 2 hours, right? An SPF of 15 means that, theoretically, you're protected for 15 times longer than you would be without sunscreen. This, of course, doesn't take into account the changes in sun exposure throughout the day as the sun changes position in the sky.
The FDA has passed new regulations recently which will go into effect next year. These will require sunscreens to show that they block UVA and UVB rays in order to be labeled "broad spectrum" and only products with an SPF of 15 or higher can claim to prevent sun damage, wrinkles, and skin cancer. Further, no sunscreen manufacturers can label products as having an SPF higher than 50 because there is not enough evidence to prove that going above an SPF of 50 increases the benefit. The term "sunblock" can no longer be used, nor can "sweat-proof" or "water-proof". Instead, a product can be labeled "water-resistant", but then must state for how long, 40 or 80 minutes.
As always, staying out of the sun, avoiding tanning beds, and covering up with hats and long-sleeved clothing are very important in order to prevent sun damage, wrinkles, and cancer. If you're concerned about your vitamin D levels, talk to your doctor about alternate sources or about safer ways to get vitamin D naturally.
For more info:
Understanding Sunscreen Products - FDA
FDA Cracks down on Sunscreen Claims, bans 'sunblock'
What IS Sunscreen?
Skin Cancer, Sun, and Sunscreen