How Does Sunscreen Work?

Posted in Skin Cancer, Skin Care | May 15, 2017

Everyone knows that the sun’s ultraviolet rays and human skin don’t get along. That’s even more so at the 3,623-foot altitude of Bend. With less atmosphere to get in the way, the UV rays are even more intense.

Sunscreens are a given today. We know that if we’re going to be out for a hike on the Sisters, skiing at Bachelor, or playing golf at Sunriver that putting on sunscreen is as important as the equipment such as hiking boots or a sand wedge.

But it wasn’t always that way. If you’re in your upper 50s or 60s now, you probably remember when the first sunscreens were introduced. The first true sunscreen was called Glacier Cream and later became Piz Buin (which still makes sunscreen lotions today), and it was developed in 1946 by a Swiss chemist. But when Coppertone (the name says it all) came on the market in the 50s, sunscreen lotion began to grow. Of course, it’s estimated now that the early Glacier Cream and Coppertone products had an SPF of 2! Not much protection there.

Today’s sunscreens have come a long way. Now they’re waterproof (for awhile) with effective SPFs of 50 (it’s thought that any SPF over that doesn’t provide any more protection).

Since we’re big fans of protecting your skin at Deschutes, here’s a little primer on how your sunscreen blocks the sun from damaging your skin.

Inorganic versus organic

Sunscreens come in sprays, lotions, gels, or waxes, and are made of a mix of chemicals. Inorganic chemicals in sunscreen can reflect or scatter the light away from the skin. Organic (carbon-based) chemicals can absorb UV rays so that your skin doesn’t.

Some of the early inorganic chemicals included minerals such as zinc oxide and titanium dioxide, and they acted as physical sunblocks. To be effective, they had to be covering the skin, hence the white noses of people on the beach in the 80s and 90s. The minerals reflected the sun’s UV rays back off the skin just as white paint reflects light. Today’s inorganic particles are much smaller, so users don’t have to look as if they’re covered with white frosting.

Organic chemicals used in sunscreens have names such as avobenzone and oxybenzone. These chemicals don’t reflect or deflect the UV rays; they absorb them. They do this with chemical bonds. As the bonds absorb UV radiation, the components of the sunscreen slowly break down and release heat. This is why these sunscreens have an effective time limit at which point the user would need to reapply.

SPF

The sun is delivering two types of ultraviolet rays onto your skin, UVA and UVB rays. UVB rays cause sunburns. For a long time, these were the only rays that sunscreens protected against, as their effects were obvious on the lobster-red skin. UVB rays affect the epidermis, the skin’s outer layer.

More recently, the effects of UVA rays have come into focus. UVA rays penetrate the epidermis into the dermis, the skin’s second layer. It’s thought that UVA rays damage the skin longer term with premature wrinkling, age spots, and other issues. UVA rays don’t cause sunburn, though, so they’re not as obvious.

SPF is how you can judge the protection level of a sunscreen. It stands for Sun Protection Factor, and it refers to how well the sunscreen protects the user against UVB rays. Obviously, SPF came before UVA rays were understood. Now, any sunscreen worth a thing is labeled “broad spectrum,” and it protects against both UVB and UVA rays.

It’s recommended to use the broad-spectrum sunscreen with SPF between 15 and 50. A sunscreen with SPF 15 protects against about 93 percent of the sun’s UVB rays; SPF 30 blocks 97 percent. No sunscreen provides a 100 percent block.

So, there’s some sunscreen information from your friends at Deschutes Dermatology. Put on that sunscreen and get out there in our beautiful Oregon outdoors. But remember to get your skin checked for skin cancer with Dr. Carter here once a year. Call us at 541-330-0900 to make your appointment.


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