Sun Protection and Sunscreens (cont.)
Are all sunscreens equally effective against UV radiation?
No. Some sunscreens protect against only one type of ultraviolet
radiation: ultraviolet-B (UVB). Others protect against both types of
ultraviolet radiation that reach earth's atmosphere from the sun: ultraviolet-B and ultraviolet-A (UVA).
Sunscreens that protect against both UVA and UVB, and are thus
classified as "broad spectrum," are recommended for everyone.
How do sunscreens work, and which sunscreen ingredients protect against both types of UV
radiation?
Physical sunscreens containing zinc oxide or titanium dioxide protect
against UVB and UVA. However, zinc oxide blocks more UV radiation than
titanium dioxide and, therefore, is the preferred ingredient. Some chemical
sunscreens can also block UVA rays. Octocrylene is a chemical known as a
cinnamate that has both UVA- and UVB-absorbing properties, and the benzophenones
(such as avobenzone) can also absorb both UVA and UVB rays. In July 2006, the
U.S. FDA approved an over-the-counter (OTC) sunscreen preparation known as Anthelios SX that
contains the UVA filter ecamsule. Ecamsule is a potent UVA-blocking compound
that has been sold in sunscreen products in Canada and Europe since 1993.
How should skin sunscreens be applied?
It's a good general rule to apply a sunscreen very liberally.
Anyone who skimps won't receive full protection. The sunscreen should
be applied about a half hour before going outside to allow time for
the sunscreen to soak
in and take effect.
Do water or perspiration wash off sunscreen?
Yes. Therefore, sunscreen should be reapplied at least every two hours when staying outdoors for a prolonged period and after swimming, bathing, perspiring heavily, or drying off with a towel or handkerchief. Water- and perspiration-resistant sunscreens are available. However, even their protection will not last indefinitely.
Next: Can sunscreens cause a skin reaction? »
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