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IS IT POSSIBLE TO SEE THE SOLAR DAMAGE CAUSED BY UVA AND UVB RAYS? WHAT DO WRINKLES LOOK LIKE UNDER THE MICROSCOPE?
Normal healthy skin is seen in the photograph to the left with pink collagen in the dermis. This is is contrast to the photograph on the right with marked solar damage. This solar damage consists of collagen which is no longer pink, but now has a bluish color. There is noticeably less collagen . This dermal collagen damage is caused predominantly by UVA rays and is responsible for the skin sagging, fine lines, loss of elasticity, skin thinning, ect. associated with chronic sun exposure.
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WHAT IS UVB AND UVA?
UVB rays produce the familiar sunburn. They also cause skin cancer. SPF (sun protection factor) ratings effectively rate the level of UVB protection provided by sun protection products. The UVB rays have a shorter wavelength meaning that they do not penetrate into the deep layers of the skin.
By contrast, UVA rays have a longer wavelength, penetrating deeper into the skin, and produce the aging associated with chronic sun exposure such as: skin sagging, loss of elasticity, pigment changes, deep wrinkles, and dry skin. Recent studies have shown a strong link between UVA rays and the development of melanoma. Critical wavelength (CW) is the international standard to rate the level of protection against UVA rays. |
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WHAT DOES SPF MEAN?
SPF (sun protection factor) measures how long it takes sunscreen protected skin to begin to sunburn (turn red) as compared to unprotected skin. For instance, if it takes unprotected skin takes 10 minutes to burn, then sunscreen protected skin with a SPF value of 15 will take 150 minutes to burn. SPF values only rates the level of UVB protection. |
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WHAT IS CRITICAL WAVELENGTH?
Critical wavelength (CW) is the most effective way to rate UVA protection. Solar radiation travels in waves. The wavelength corresponds to the solar energy of the wave. Solar radiation of 290nm to 400nm (the UVB-UVA range) is reproduced in a laboratory device designed to measure the amount of radiation absorbed by a sunscreen. Starting at the beginning of the UVB range (290nm), progressively higher wavelengths of light are aimed at the sunscreen. The point at which the sunscreen lets 10% of the radiation through is defined as the critical wavelength. The higher the number, the better. A sunscreen with a critical wavelength over 370nm is considered by the FDA to provided good UVA protection. LUCA, with a critical wavelength of 383nm, provides the best UVA protection available. |
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WHAT IS AVOBENZONE AND WHY IS IT IMPORTANT?
Avobenzone is the best UVA filter available. It, along with zinc and titanium dioxide, are the only compounds which are FDA approved for protection against UVA rays. Consumers often say that zinc and titanium dioxide formulations feel “heavy.” Avobenzone formulations by comparison are light and cosmetically elegant. The highest critical wavelengths(CW) are also achieved in formulations using stabilized avobenzone. LUCA with a CW of 383nm, has the highest critical wavelength of any product on the market. |
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WHAT DOES “STABILIZED” AVOBENZONE MEAN?
Although Avobenzone is a superior UVA absorber, it is a photounstable compound, meaning that it breaks down quickly in sunlight. It is necessary for formulations using avobenzone to be stabilized. LUCA uses Polycrylene® (CPH Innovations) to stabilize avobenzone. Manufactures not only need to provide a critical wavelength to rate UVA protection, but this measurement should be performed on specimens which have been irradiated to simulate 4-6 hours in intense sunlight, proving that the formulations have been effectively stabilized. |
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WHEN SHOULD YOU USE A SPF15 AS OPPOSED TO A SPF30?
A SPF of 15 will absorb approximately 94% of the UVB rays with a SPF of 30 absorbing approximately 97% of the UVB rays. This means that by wearing a SPF of 15, one can remains in direct sunlight for 2 hours before beginning to sunburn. Wearing a SPF of 30 will increase this time in the sun to 4 hours before a sunburn begins. This extra protection is achieved with a significant increase in the levels of active ingredients, which some individuals find to be irritating to the skin. It is best to use a moisturizing SPF 15 formulations everyday, with the use of a SPF30 for times of intentional sun exposure. |
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WHY NOT USE A SPF 45 OR HIGHER IF SUN PROTECTION IS SO IMPORTANT?
An SPF 15 blocks 94% of the UVB rays with a SPF 30 blocking approximately 97% of UVB rays. After reaching a SPF level of 30-33, the effectiveness of UVB filters begins to plateau. Increasing SPF values above 30 requires one to markedly increase the levels of active ingredients. With increasing levels of active ingredients, one is increasingly likely to experience irritation.
In 1999, the FDA proposed a final monograph regulating sunscreens where SPF levels were limited to 30. SPF values above 30 could only being state as 30+. The reasons for this decision were concern by some that the test methods for determining SPF values begin to loose predictive value when testing formulations with SPF's over 30. One can see this when performing a SPF test. The range of values obtained from the 20 test subjects is greater for a SPF 30 than for a SPF 15 or an SPF of 4.
The FDA never approved the Final Monograph of 1999, leaving manufactures to largely do whatever they pleased as far a SPF values were concerned. The result has been a plethora very high (SPF 30 and over) sunscreens. The FDA is now proposing sweeping new changes in sunscreen regulations and may approve SPF claims up to SPf 45.
We recommend that consumers follow the FDA final monograph and not use sunscreens with SPF values over 30. If the FDA approves higher SPF values in the future, and implements testing guidelines to back up these claims, then we would change our recommendations accordingly.
The FDA has also considered high SPF value to potentially give consumers "a false sense of security", encouraging them to stay out longer in the sun, and not reapply sunscreen as often as necessary. This is perhaps the best take home message. Reapplication is more important than SPF values and one should reapply every two hours if exposed to water or sweating. |
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©
2008
Island Air, LLC
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