Stop the Burn

By Dr. Diane Baker

Exercising outdoors is especially pleasurable on a warm sunny day. But sunshine is a double-edged sword: while it can definitely add to your sense of well being, it also poses a problem for your skin. When ultraviolet (UV) rays from the sun hit the skin, they produce an acute injury that results in sun damage or sunburn. Chronic exposure to the sun’s rays leads to photoaging — wrinkles, blotchy or freckle- like brown spots, roughness, and a general leathery look — and skin cancer.

Before considering the ways to protect ourselves from sun damage, let’s discuss what benefit, if any, there is to getting a tan. Certainly as a culture we have long viewed tanned skin as more attractive than pale skin. Some of my dermatology patients tell me they like to get a “base” tan either by exposure to natural sunlight or in a tanning bed early in the summer so that they will not sunburn with subsequent sun exposure. They ask if it’s better to do that than to sunburn. I tell them that while it is true that a sunburn represents a more severe insult to the skin than a sun tan, it is also true that tanning is your skin’s reaction to damage that has already occurred from ultraviolet light. When ultraviolet radiation hits the skin a complex series of events occur that result in inflammation, DNA damage, suppression of the skin’s immune defense system, and a decrease in the skin’s ability to repair damaged DNA. All of this leads to increased risk of skin cancer. In fact, ultraviolet light is considered a complete carcinogen, not just a partial one, because it both causes DNA damage and reduces the body’s ability to repair that damage. Moreover a UV-induced tan only confers a sun protection factor (SPF) of 2 or 3 against sunburn only, not against DNA damage.

Once this is understood it is clear that our goal should be to prevent exposure to UV as much as possible, not to give our skin a little UV damage and induce a tan so that we can get more UV damage without burning.

So how do we protect ourselves? The American Academy of Dermatology and the Skin Cancer Foundation recommend the following guidelines to limit exposure to UV rays from the sun:

• Exercise outdoors before 10am or after 4pm if possible. The sun’s rays are strongest between those hours.
• Walk or exercise in the shade whenever possible.
• Wear protective clothing and sunscreens.

To make sense of the myriad of options available in sunscreen and sun protective clothing one must understand the concept of the sun protection factor rating or SPF.

Sunscreens protect by absorbing, reflecting, or scattering ultraviolet light away from the skin. They reduce the amount of UV that penetrates the skin but some rays do get through. The SPF of a product lets us know how well it will protect us from sunburn. A sunburn is predominantly the result of exposure to the short wavelength portion of the sun’s ultraviolet rays, the UVB ray. The longer wavelength sun UV rays, or UVA, also cause damage and actually penetrate deeper in the skin than do the UVB rays. Currently there are no effective and reproducible ways of measuring protection of sunscreen ingredients against UVA. But sunscreens that are labeled broad spectrum protect against both UVA and UVB rays.

Dermatologists recommend using a sunscreen with a SPF factor of at least 15, applying it to skin that will be exposed to the sun 1/2 hour before exposure, and reapplying it every two hours. One ounce of sunscreen (enough to fill a shot glass) is the amount needed to cover the exposed areas of an average adult’s body.

A sunscreen with a SPF 15 will prevent a person’s skin from sunburning 15 times longer than it would take that skin to sunburn without the sunscreen. It may take only 10 minutes for fair skin to sunburn in the noonday sun without protection. It would take 150 minutes for that same skin to sunburn under the same conditions if a SPF 15 sunscreen were applied properly.

Realize that the sunscreen’s protection does not increase proportionally with the SPF number. An SPF 30 sunscreen does not offer double the protection of an SPF 15 sunscreen. An SPF 15 means about 93% of the UVB rays are absorbed or scattered and a SPF 30 means about 97% are deflected. This is why dermatologists agree that an SPF 15 is adequate in most situations. Conversely the amount of protection falls off dramatically with SPF numbers less than 15.

Sunscreen ingredients that offer good broad-spectrum coverage are oxybenzone, avobenzone (or Parsol 1789), octylmethyl cinnamate, and sulisobenzone. Titanium dioxide and zinc oxide are broad-spectrum sunscreen ingredients that are physical sun blockers. The newer formulations of these ingredients are less opaque than the old zinc oxide, so they don’t look like white paste on the skin. They are especially good for people with sensitive skin.

Wearing sun protective clothing is important for outdoor activities involving long periods of sun exposure. Companies such as Sun Precautions and the Sun Protective Clothing Company offer clothing made of fabrics that are light but tightly woven so that they provide sun protection equivalent to an SPF 30 or greater.

Typical summer weight T-shirts provide an SPF of only 5 to 9 and even less when wet. Adding SunGuard™ laundry treatment to the wash cycle can increase the SPF of regular clothing. This treatment is safe for all washable fabrics and will continue to be effective through several washings. A single treatment can increase the SPF of a typical white T-shirt from 5 to 30. It will not add sun protection to 100% polyester or acrylic fabrics however. SunGuard™ can be purchased in most grocery stores where fabric dyes are sold.

With innovative sun protection products and common sense, it is much easier now to protect your skin from the sun than it was in the past. Protecting your skin now will pay off by keeping your skin healthy and younger looking just as your exercise program keeps the rest of your body strong and healthy.

Dr. Baker is in full-time private practice in Portland. She holds a clinical appointment as a Clinical Professor, Department of Dermotology, at Oregon Health Sciences University in Portland.