(MayoClinic.com) If you're like most people, you enjoy spending time outdoors and feeling the heat of the sun on your skin. But not all the sun's rays are pleasing. Ultraviolet (UV) light — invisible, but intense rays from the sun — can damage your skin and increase your risk of skin cancer.
Though it's not the only safeguard you need to take, sunscreen is one of the easiest ways to protect your skin and is a good first line of defense.
Here's how you can get the most protection from your sunscreen.
Sunscreen absorbs, reflects or scatters UV light. It's divided into three wavelength bands — ultraviolet A (UVA), ultraviolet B (UVB) and ultraviolet C (UVC). Only UVA and UVB rays reach the earth.
Sunscreens provide either physical or chemical protection from UV light.
If you spend time outdoors during daylight hours, you need to use sunscreen even if you have darker skin pigment, tan easily and can tolerate longer periods of sun exposure without burning. Regardless of skin type, the sun's energy penetrates deeply into the skin and damages DNA of skin cells. This damage may ultimately lead to skin cancer.
Children are especially susceptible to the harmful effects of the sun, so take extra steps to protect their skin and to prevent sunburns. Babies younger than 6 months should be kept out of direct sunlight because their skin is even more fragile. Use sunscreen on an infant only if you're unable to keep him or her out of the sun and are unable to cover exposed skin. Use a small amount on uncovered areas, such as on hands or ears, and check for any skin reactions.What is an SPF?
All sunscreens products include an SPF, which stands for sun protection factor. The SPF number is a measurement of the amount of UVB protection — the higher the number, the greater the protection. Currently, there's no standard rating system that measures UVA protection.
SPF is not an indication of how much time you can spend in the sun. For example, if you use a sunscreen with an SPF 30 rather than one with an SPF 15, it doesn't mean you can stay in the sun twice as long. In reality, an SPF of 15 filters out about 93 percent of the UVB rays; SPF 30 filters about 97 percent of UVB rays. The beneficial effects of sunscreen decreases over time, so after a few hours the difference between the two may be even less.
Don't rely on the SPF factor to decide how long you're safe in the sun. And don't count on your skin to tell you when you've had too much sun. It may take up to 24 hours for a sunburn to develop fully.What reduces the effectiveness of sunscreen?
How much protection your sunscreen offers depends on many factors, including how likely your skin is to burn (your skin type), the amount and type of sunscreen used, how often the sunscreen is applied, and how intense the UV rays are.
In addition, many factors can make sunscreen less effective. These include:
Not all sunscreens are the same. Be sure to:
Most people use sunscreen too sparingly. A liberal application is 1 ounce (29 milliliters) — the amount in a shot glass — to cover all exposed parts of the body. If you have a 4-ounce (118-milliliter) bottle, you'll be using about one-fourth of it for one application. Be sure to rub the sunscreen in well.
To maximize protection, apply sunscreen liberally 30 minutes before going outdoors and reapply every two hours, or sooner as needed.Is sunscreen enough to protect your skin?
Though it offers some protection, no sunscreen blocks out all of the UV rays. Therefore, sunscreen shouldn't replace other protective measures, such as limiting the time you spend in the sun and covering your skin. For the most complete sun protection, use all three of these methods:
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