Planning some fun in the sun? You don't have to spend big bucks on sunscreens and high SPF levels to get good protection.

If your sunscreen meets the American Academy of Dermatology's recommendations -- it's water resistant, has an SPF of at least 15, broad-spectrum coverage against UVA and UVB light, the proper ingredients, and you reapply a one-ounce amount frequently -- you should be good to go, even with a cheaper store brand. Some dermatologists recommend using at least SPF 30.

One thing to watch out for is UVA-ray protection since SPF only applies to UVB rays, says Henry Lim, chairman of the department of dermatology at Henry Ford Hospital in Detroit.

The Food and Drug Administration doesn't have a UVA rating yet, he says, so while sunscreens may claim broad-spectrum protection, you may not be getting strong protection from UVA rays. He suggests using products containing avobenzone （also called Parsol 1789）, titanium dioxide or zinc oxide.

As for SPF 100? If you're outdoors on a sunny day, "SPF 50 is probably sufficient," says Dr. Lim. "Beyond 30, the increase in the filtering is small."

SPF 15 blocks 93% of UVB rays, SPF 30 blocks 97%, and protection doesn't increase proportionately with a higher SPF number, according to the American Academy of Dermatology （aad.org）.

想要在户外活动吗？你不必为了获得好的防护效果而花很多钱在防晒品和高的防晒系数上。

如果你的防晒品和美国皮肤医学研究院所推荐的一样，防晒系数最少在15以上、能够同时地域uva和uvb两种紫外线、成分适当并且你能够频繁涂抹，那么你就可以尽情的享受户外活动，即便它不是什么大品牌。皮肤专家大多推荐防晒系数在30以上的防晒品。

uva即生活紫外线的防护是需要注意的，因为防晒系数仅仅适用于uvb即户外紫外线的防护，底特律州亨利福特医院的皮肤科主任亨利。李这样说道。他指出，食品和药物管理部门还没有uva的评定等级，因此当防晒品要求有比较广泛用途时，它就可能对uva的防护作用很小。他建议选择含有一种叫作阿伏苯宗或者巴松1789的物质，和钛的二氧化物或者锌的氧化物的成分的防晒产品。

对于防晒系数100的呢？如果你的户外活动是在晴天，"防晒系数50就非常适当了，"李医生说。"防晒系数超过30,过滤紫外线功效方面的增益就很小了。"