If you've already read our The Sun and Your Skin and What Your Sunscreen Label Tells You, you already know more than the average consumer about how sun damage happens and what the FDA is doing to make safeguard you from marketing ploys when buying sunscreen. So what's left to know?
How sunscreen works to protect you from sun damage. Sunscreens protect by either blocking or absorbing harmful UV radiation before it has a chance to damage your skin cells and matrix.
Physical Protection
Some sunscreen ingredients protect your skin from UV radiation by physically blocking it providing a protective barrier between the sun and your skin. Physical blockers include zinc oxide and titanium dioxide. Of the two, zinc oxide provides the best protection because it has been shown to block nearly the entire UV-A and UV-B spectrum. Kind of makes you re-think making fun of the lifeguard's white nose, doesn't it?
Chemical Protection
Other sunscreen ingredients protect your skin by absorbing UV radiation, which stops the UV penetration at the epidermis level before it can damage deeper skin layers. Chemical sun protection is a bit tricky. Because chemicals absorb UV radiation, the sun protection stuff can itself become unstable and degrade, lessening their effectiveness. That's why it's so important to reapply sunscreens according to the instructions on the label. Reapplying sunscreens per instructions (and after you've been swimming or sweating a lot, even if the label says water resistant) ensure that you continue to have adequate sun protection.
What SPF Really Means
SPF, or Sun Protection Factor, is the standard used to measure how well a sunscreen protects against UVB rays, the rays most closely associated with sunburn. In simple terms, SPF is based on how much longer skin can be exposed before burning when sunscreen is applied as directed. But SPF is not a straight-line scale of protection. An SPF 15 blocks about 93% of UVB rays on average, while SPF 50 blocks about 98%, so very high SPF numbers do not increase protection as dramatically as many people assume.
It is also important to remember what SPF does not tell you. SPF ratings focus on UVB protection, but UVA rays can contribute to deeper skin damage and long-term skin concerns. That is why broad-spectrum sunscreens matter: they help protect against both UVA and UVB exposure.
The Protection is in the Dose
The SPF indicated on a sunscreen product, whether provided by physical blockers, chemical absorbers or both, is only achieved if the right amount of sunscreen is used. Although most sunscreen labels aren't very specific, they mean it when they say apply generously. On average, to adequately protect your body from head to toe, you need a full ounce of sunscreen that's a blob about the size of a golf ball! And that's per application.
For most people, a broad-spectrum sunscreen with at least SPF 30 is a smart choice. What matters just as much as the number on the bottle is proper use: apply complete coverage before going outdoors, and keep reapplying during longer periods outside. Even a high SPF sunscreen will not do much good if you skimp on it or forget to put more on.
Psychological Protection?
Perhaps one of the most valuable protections sunscreens may offer is peace of mind. When you are adequately slathered in sunscreen, experts agree that you are free to enjoy your fun in the sun without the nagging fear that skin cancer is creeping up on you. At the same time, don't get too comfortable in the sun after your initial sun protection coating. Set a timer to remind you to reapply, and don't skimp. Saving an ounce of sunscreen isn't worth the wrinkles spots or worse as reminders of sunscreen frugality. Safely enjoy the Memorial Day weekend introduction to summer!'
