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　　Q. Whats the Difference Between a Sunscreen and a Sunblock?

　　Sunscreens are the most popular at the moment. Available in creams, lotions and gels, they contain chemicals that absorb UV rays. They are also inconspicous on the skin. The chemicals that are most often found in sunscreens include PABA, Benzophenones, Cinnamates, Salicylates,

　　Sunblocks instead of absorbing UV rays, reflect them. At one time sunblocks could be spotted by the opaque white film, but new technology has created sunblocks with particles so tiny, that the opaque film in no longer noticeable. Chemicals most common in sunblocks include Titanium dioxide and zinc oxide。

　　据国际合众社消息  美国一项报告说，多数人不清楚防晒乳和遮光剂的区别。

　　哈佛医学院一项研究解释，防晒乳反射阳光，因此阻止光线到达皮肤；遮光剂吸收紫外线要多于反射紫外线。

　　防晒乳比如氧化锌，二氧化钛，能有效保护皮肤免受UVA 和UVB伤害，这两种紫外线能导致晒伤和皮肤癌。

　　防晒乳在皮肤上呈白色，而遮光剂一般无色。遮光剂的主要缺点是在日光照射几个小时以后就分解了，需要重新涂抹。

　　美国皮肤病学会建议使用SPF值低于15的遮光剂，但如果皮肤特别好，或者患皮肤癌的几率比较高，可以选择SPF值更大的遮光剂。SPF值越大，保护的时间越长。

　　报告说，贴有广谱标签的产品一般含有多种防晒成份，对不同波长紫外线都有保护作用。