Thursday, July 5, 2007

SPF, UVB and UVA: What Does it all Mean?

We all know that one of the most important things you can do to protect yourself from the sun is to regularly use sunscreen. Experts say you should use a sunscreen with SPF 15 anytime you are going to be exposed to the sun for more than 10 minutes. Studies have shown that using SPF 15 everyday provides more protection than using a higher SPF intermittently.

But, How does Sunscreen Work?
The letters SPF stand for Sun Protection Factor, but there are still moderate discrepancies as far as what exactly the numbers indicate. Many sources say that the SPF number is directly correlated to a specific amount of time a person has before they start to burn. Really, the only thing that is known for sure is that the higher number, the more protection. For all practical purposes, an SPF number should be thought of as a general scale to evaluate the level of protection.

A good sunscreen will block exposure to both UVB and UVA rays. They do this by breaking down collagen, creating free radicals, and inhibiting the natural repair mechanisms of the skin. Neither UVA or UVB rays are visible, but both can separately cause damage to the skin. UVB rays, or ultraviolet light, type B, can cause cellular damage to outer layers of the skin, drying and aging the skin. They penetrate into the deepest cell layers of the epidermis and are the main cause of sunburn, DNA-damage and the development of skin cancer. UVA rays, or ultraviolet light, type A, penetrate deeply into the connective tissue. They cause immunosuppression and chronic light-induced damage. UVA rays are also responsible for phototoxic as well as photoallergic reactions.

Nearly all sunscreens provide some level of protection against UVB rays, though no product yet screens out all UVA rays. SPF sunscreen numbers indicate sunburn protection from UVB rays only. No rating system yet exists for UVA, but if you check the ingredients, the presence of avobenzone, titanium dioxide, or zinc oxide indicate that the sunscreen protects from both.

Experts stress the importance of using the recommended amount and re-applying at the correct intervals. Most people only apply 25% to 50% of the recommended amount, so read directions carefully. Sunscreen needs time to penetrate the skin, so it is essential to apply it one-half hour before going out in the sun, and should be reapplied every 2-4 hours, or immediately after swimming, excessive sweating, or toweling.

If you want to keep yourself protected from the sun at all times, avoid being in direct sunlight between the hours of 10 am and 3 pm, wear tight-weave clothing that covers your body, as well as a hat—and wear sunscreen!

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