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The Lowdown on SPF

by Staff Writer
The ultraviolet rays of the sun are responsible for 86 percent of all cases of melanoma, the deadliest type of skin cancer, and for 90 percent of all other types of skin cancer. Sunscreen is your main line of defense against the harmful effects of the sun, but in order to ensure that you fully protect your skin, you need to choose the right sunscreen formula. One of the most important considerations that you'll need to make when choosing a sun care product is which Sun Protection Factor or SPF is right for your skin. But just what is SPF? How can you know which degree of SPF is best? Get the full lowdown on the SPF rating system.

What SPF Tells You

The SPF level of a sunscreen is a measure of how much of the sun's ultraviolet B (UVB) rays the formula absorbs or reflects. UVB is a form of ultraviolet energy that is very intense and that comes in short waves. When you're exposed to the sun with no protection on your skin, it's the UVB in sunlight that causes the skin to become irritated and sunburned. In addition, the radiation from UVB can contribute to the mutations that develop into skin cancer. When you compare SPF levels of sunscreens, those with higher numbers block more UVB than those with lower numbers.

What SPF Doesn't Tell You

Sunlight contains more than one type of ultraviolet energy. Ultraviolet C (UVC) rays are also found in sunlight but are very short in length and do not reach the Earth in large enough amounts to make it necessary to protect your skin from their effects. Ultraviolet A (UVA) rays are longer, less intense waves that travel through the atmosphere and can penetrate your outer layer of skin. While UVA rays don't cause sunburn, they do damage the skin cells. It's this type of radiation that damages proteins in the skin and contributes to sun-related wrinkles and lines. In addition, UVA is a major factor in the development of skin cancer. The SPF of a sunscreen does not tell you how much UVA a sunscreen provides. In fact, unless a sunscreen is described as "broad-spectrum" on its packaging, it may not provide any UVA protection at all.

How to Choose the Right SPF

Most skin care experts recommend a broad-spectrum sunscreen with an SPF of at least 15 for daily use. SPF 15 sunscreens block 93 percent of UVB. For prolonged exposure to the sun, the recommended minimum SPF level is 30, which can filter out 97 percent of UVB. While sunscreens with higher SPF levels protect against more of the sun, the increases are very slight. For example, an SPF 50 sunscreen only protects against 1 percent more of the UVB than SPF 30 at 98 percent. To choose the right SPF level, you'll need to take into consideration how fair your skin is and whether or not you use any skin care products or take any medications that increase your sensitivity to the sun. Your doctor can help you decide precisely how much UVB protection you need and recommend the right SPF level for you.