What are SPF Sunscreen Ratings Anyway?
SPF, or Sun Protection Factor, is a measurement of how well a sunscreen will protect skin from the sun’s harmful rays, the kind of radiation that causes sunburn and is thought to contribute to some types of skin cancer.
If your skin would normally burn after 10 minutes in the sun, applying an SPF 15 sunscreen would allow you to stay in the sun without burning for approximately 150 minutes (a factor of 15 times longer). This is a rough estimate and depends on skin type and intensity of sunlight. For best protection, dermatologists strongly recommend using a sunscreen with a minimum SPF rating of 15, and applying sunscreen generously and frequently year-round for all skin types.
Consumers need to be aware that SPF protection does not increase
proportionally with an increased SPF number
SPF is not quite that simple, the scale is not linear. SPF15 sunscreen blocks about 93% of UVB rays, SPF30 sunscreen blocks about 97% of UVB rays and an SPF50 blocks 98% of UVB rays. So SPF30 sunscreen does not give you twice the protection of SPF15 sunscreen! The beneficial effects of sunscreen decreases over time, so after a few hours the difference between the two may be even less.
The difference between a SPF 15 and a SPF 30 sunscreen may not have a noticeable difference in actual use as the effectiveness of a sunscreen has more to do with how much of it is applied, how often it is applied, whether the person is sweating heavily or being exposed to water.
And an SPF50 sunscreen is only 1% more effective than an SPF30 sunscreen. In fact, the FDA (the US agency that governs drugs like sunscreens) does not allow any sunscreen to be labeled as anything higher than SPF30+ because they know that higher SPF sunscreens do not offer significantly greater protection, and that such products are misleading to consumers. Currently any sunscreen labeled with and SPF greater than 30 (or without a ‘Drug Facts’ label) is ‘misbranded’ under Section 502 of the Federal Food, Drug & Cosmetic Act.
If you are fair-skinned and sunburn easily, you may want to select a sunscreen with a higher SPF to provide additional protection. Using a cream, oil or lotion is a matter of personal choice, but keep in mind that most oils do not contain sufficient amounts of sunscreen and usually have an SPF of less than 2─ filters out about 50 percent of the UVB rays. All sunscreens need to be reapplied, so follow the guidelines written on the sunscreen bottle. Gel sunscreens tend to sweat off and, therefore, need to be reapplied more frequently. Remember, expensive sunscreens are not necessarily of better quality.
What is actually UVA, UVB and UVC?
The sun’s ultraviolet (UV) light falls into three wavelength bands:
UVA RAYS: Long-wave solar rays of 320-400 nm. UVA penetrates the skin more deeply into the Dermis─2nd layer of skin, where collagen, the structural scaffolding of the skin, is located. This causes the skin to sag in places leading to photo aging, actinic damage (wrinkled, leathery, variously pigmented skin); and can contribute to skin cancers including melanoma. Rays are the same strength year-round.
UVB RAYS: Short-Wave solar rays of 290-320 nm. UVB is about 90% absorbed within the epidermis and essentially no UVB penetrates deeper than the upper dermis.
Cause sunburn and considered to be the main cause of basal and squamous cell carcinomas, as well as a significant factor in melanomas. These rays break down the organization of skin cells, causing wrinkles and broken blood vessels.
UVC Rays: Shortest wavelength and are usually absorbed by the ozone layer.
Astronauts and pilots are more frequently exposed to UVC rays. As the ozone layer thins, attention will need to be paid to these UVC rays.
Lines, dark spots, and uneven skin texture are not the inevitable effects of aging but are often the result of too much sun exposure. Overexposure to sunlight can also cause skin cancer. The only way to prevent premature aging and skin damage as the result of overexposure is to stay out of the midday sun when possible, wear protective clothing and hats, and always use the proper sunscreen.
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