Living on the islands, with our endless sunny days, we’re all exposed to a lot of sun. The sun’s ultraviolet rays are the problem, penetrating the skin and damaging its cells, leading to skin aging and wrinkling, and various skin cancers.
We all know that the best thing would be to never go outdoors, unless we are dressed like a mummy. But when you live in a tropical wonderland like Hawaii who wants to do that?
So, we all apply sunscreen. But what do you really know about sunscreen and how it protects, or doesn’t protect, you? Here’s some info.
Sun protection factor (SPF) and UV radiation
Since the advent of modern sunscreens (post Pre-Sun, for those of you in your 50s!), a sunscreen’s efficacy has been measured by its sun protection factor, now commonly known by its acronym, SPF. SPF is not really a measure of protection, it is a measure of how long it will take for ultraviolet B (UVB) rays to redden your skin compared to having no sunscreen on. For instance, SPF 15 means that it will take 15 times longer to get burned at the beach with sunscreen on than without. Why does it use the UVB rays? Those are the rays that cause sunburn because they penetrate only the epidermis, the surface layer of the skin.
As for amount of UVB protection, an SPF 15 sunscreen screens 93 percent of the sun’s UVB rays; SPF 30 protects against 97 percent; and SPF 50 protects against 98 percent. The U.S. Department of Health and Human Services recommends only SPF 15 and higher for providing adequate protection.
But scientists now say UVA rays, which penetrate far more deeply, into the dermis layer of the skin, also cause skin damage and skin cancer. So, you need a sunscreen that protects against both UVA and UVB. To do this, look for a sunscreen with at least SPF 15, plus some combination of the following UVA-screening ingredients: avobenzone, ecamsule, oxybenzone, titanium dioxide, and zinc oxide. When you see a label that says broad spectrum or multi spectrum or UVA/UVB these indicate that some UVA protection is provided. However, there isn’t a measure of how much protection these terms denote.
How do sunscreens work?
Sunscreens aren’t really a screen as you would think of it, simply blocking the sun’s rays. They really are more like a mirror. The ingredients in sunscreens form a thin, protective film on the surface of the skin and absorb the UVA radiation before it penetrates the skin. The “sunscreens” are actually physically rejecting the sun, meaning that their insoluble particles reflect the UV rays back off the skin. The FDA has approved 17 active ingredients for use in sunscreens.
Unfortunately, no matter how much you know about UVA rays and sunscreen, your skin will still suffer sun damage. That’s where we come in at Matsuda. Drs. Matsuda and Sheu have extensive experience diagnosing and treating sun damage, whether it be skin cancer or less extreme damage. Be sure to have your skin checked at least yearly because where we live the sun just keeps on keeping on. Call us for an appointment, 808-949-7568.