Sunsense Means Sunblock

Cellular Skin Changes Caused by UV Radiation

Sunlight has a profound effect on the skin and can cause premature skin aging, skin cancer, and other skin changes. Exposure to ultraviolet light from sunlight accounts for 90% of the symptoms of premature skin aging. Some skin changes commonly assumed to be "just part of getting older", like an increased tendency to bruise, are often related to prolonged exposure to UV radiation.

What is UV Radiation?

The sun gives off invisible radiation we divide into 3 categories
based on wavelength.

  • UVC - 100 to 290 nm - "C" is most dangerous but is blocked by atmosphere
  • UVB - 290 to 320 nm - "B" causes most of sunburn redness
  • UVA - 320 to 400 nm - "A" causes most of skin aging, contributes to melanoma

Sunscreens

The first effective sunscreen was invented in 1944 and issued to soldiers fighting in
World War II. Serious sunburn was a significant problem so an American pharmacist named Benjamin Greene created a reddish, petroleum-based substance that gave
soldiers at least some degree of protection from the sun's harmful rays. Modern
sunscreen products have much higher protection factors, are far less greasy and can
be made relatively water-proof.

Sun protection factor (SPF)

 SPF stands for Sun Protection Factor. An SPF rating is calculated by comparing the amount of time needed to produce a sunburn on protected skin to the amount of time needed to cause a sunburn on unprotected skin. If a fair-skinned person normally turns red after 10 minutes in the sun, wearing the correct amount of SPF 2 sunscreen would increase the "redness" time to 20 minutes (10 min x 2). An SPF 15 sunscreen would increase the redness time to 150 minutes (10 min x 15).

Picking the Proper Sunscreen

The SPF measures the amount of UVB absorption but not UVA because UVA does not cause pain or redness. The only way to determine if a sunscreen protects well against both UVA and UVB is to check the product label. A good broad-spectrum sunscreen effective against UVA should have an SPF of at least 15 and contain either zinc oxide, titanium dioxide or avobenzone.

Apply Sunscreen Correctly

Sunscreen should be applied liberally to all sun-exposed areas. It
takes some time for sunscreen to be absorbed by the skin, so it
should be applied at least 30 minutes before going out in the sun. When applying sunscreen to the face, it's important to realize that water-based foundation or moisturizers can cause sunscreens to
break down just like sweating does. To minimize breakdown, apply sunscreen after any other water-based products are applied. Sunscreen should be reapplied after 2-3 hours in the sun or after swimming, toweling off or heavy sweating.

Make sure to apply enough sunscreen initially to reach the product's stated SPF rating. Even if you use an SPF 30 sunscreen, it might only result in an SPF
of 15, depending on how much is applied. Covering the area to be protected with a thin, unbroken film of sunscreen is normally the correct amount.

What about vitamin D?

Though excessive sun exposure is linked to some forms of skin cancer and signs of premature aging, there is evidence that vitamin D may actually help prevent other forms of cancer. While it is true that reduction in sun exposure can inhibit the production of vitamin D by the skin, fifteen minutes per day of direct exposure to the sun is generally seen as adequate for vitamin D production.


 Other recommendations

  • Since UVA rays are prevalent all year long, a sunscreen of at least SPF 15 should be worn on a daily basis to help prevent cumulative damage to the skin.
     
  • UV rays are most intense when the sun is directly overhead. When possible, limit sun exposure during the hours from 10 AM to 4 PM.
     
  • Protective clothing, such as wide-brimmed hats, UV 400 sunglasses, and tightly woven clothes with long sleeves and long pants should be worn whenever possible.
     
  • A high amount of UV is transmitted through glass, including car windshields. If you drive frequently during the hours of 10-4, consider adding a UV blocking film to
    your car windows.
Sources:  
1. American Dermatology Association  
2. American Medical Association  
     
Vision & Health Newsletter courtesy of:
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Dr. Philip Smith & Associates
1855 1st Ave #100
San Diego, CA 92101

619-297-4331