高SPF值的防曬霜并不會(huì)真的保護(hù)皮膚

　　It makes sense in theory: If you’re super pale and you burn easily, you should use the highest SPF you can find when you go out in the sun, right? Not necessarily. The reality of what various SPFs offer in the way of protection — and which ones you should be using — is a bit more complicated than that.

　　理論上是這樣的：如果你皮膚很白，但又容易曬傷，出門時(shí)就應(yīng)該涂抹高防曬系數(shù)（SPF）的防曬霜，對(duì)嗎？其實(shí)不然，不同SPF值的防曬霜都有什么作用，你應(yīng)該選擇哪種防曬霜，這些問題比你想得要復(fù)雜。

　　Sunscreens can offer protection from two types of ultraviolet (UV) rays: UVB, which according to the Skin Cancer Foundation, are the chief cause of sunburn and play a key role in the development of skin cancer, and UVA, which penetrate the skin more deeply and are largely responsible for skin aging and wrinkling, as well as skin cancer risk.The SPF measurement on sunscreens refers specifically to the UVB protection level — and the number may not mean what you think it does. SPF 15 doesn’t protect you from 15% of UVB rays, just as SPF 100 doesn’t protect you from 100% of the rays. In fact, as you get into the higher numbered SPF sunscreens (think: 50 and above), the difference in UVB protection is actually pretty minimal. “The relationship is not a linear thing,” dermatologist Dr. Mona Gohara, MD tells Teen Vogue. “For example, [SPF] 15 isn’t blocking out half of 30.” Rather, as Dr. Gohara explains, SPF 15 blocks about 93% of UVB rays, SPF 30 blocks about 95%, SPF 50 blocks about 97%, and SPF 100 blocks about 99%.

　　防曬霜可以隔離兩種紫外線（UV）：第一種是紫外線B光譜（UVB）。皮膚癌基金會(huì)的研究表明，這種紫外線是導(dǎo)致曬傷的主要原因，并且是皮膚癌的主要誘因。另一種是長波紫外線（UVA），這種紫外線會(huì)穿透皮膚，導(dǎo)致皮膚老化并出現(xiàn)皺紋，當(dāng)然也有誘發(fā)皮膚癌的風(fēng)險(xiǎn)。防曬指數(shù)SPF的測量主要是依據(jù)該防曬霜隔離UVB的能力，SPF數(shù)值的意義可能和你想的不同。SPF數(shù)值為15并不意味著這個(gè)該防曬霜可以隔絕15％的UVB，正如SPF為100的防曬霜并不是能夠完全隔絕UVB一樣。事實(shí)上，SPF值比較高（大于等于50）的防曬霜，它們隔絕UVB的能力是大同小異的。馬里蘭州的皮膚病博士Mona Gohara告訴《Teen Vogue》時(shí)尚雜志說：“二者并不呈現(xiàn)線性關(guān)系。比如，SPF值為15的防曬霜并不是隔絕15％的紫外線，反之，它可以隔絕93％的UVB。SPF值為30的防曬霜可以隔絕95％的UVB，SPF值為50的可以隔絕97％的UVB，而SPF值為100的可以隔絕99％的UVB。”

　　That said, though the UVA protection isn’t technically represented by the SPF number on a sunscreen bottle. Steven Q. Wang, MD, a dermatologist and spokesperson for the Skin Cancer Foundation, tells Teen Vogue that the difference in UVA protection between a broad-spectrum (which represents both UVB and UVA protection) SPF 50 and an SPF 100 sunscreen, for example, may be significant enough to make the increase worthwhile. “If you’re looking at SPF 50 versus 100, the...incremental benefit [of the higher one] is small, but the UVA protection may be much higher,” he says.

　　也就是說，SPF系數(shù)并不能代表隔絕UVA的能力。馬里蘭州皮膚專家及皮膚癌基金會(huì)的發(fā)言人Steven Q. Wang向《Teen Vogue》雜志透漏，在廣譜（代表UVB和UVA的隔絕能力）中，SPF50和SPF100的UVA隔絕能力是差別巨大的。也就是說，如果你在比較這兩種防曬霜，SPF值高的可能在UVB防護(hù)上沒有什么大差別，但是UVA的隔絕能力會(huì)高很多。

　　So, theoretically, though the increase in UVB protection with a super-high SPF sunscreen may be negligible, it may help, and certainly can’t hurt, to use it — that is, as long as you do so correctly. “The only downside [of using a higher SPF] is if you’re lulling yourself into a sense of false security,” Dr. Gohara says.

　　因此，理論上說，防曬霜的SPF數(shù)值增高并不會(huì)在其UVB的隔絕能力上增加多少，但是使用一個(gè)SPF值高的防曬霜還是有幫助的。只要學(xué)會(huì)正確使用，就不會(huì)有害處。Gohara 指出：“SPF值高的防曬霜唯一的缺點(diǎn)就是會(huì)給你營造一種虛假的安全感。”

　　Indeed, as Dr. Wang also pointed out, when people opt for increased SPFs, they may actually feel so protected by the product that they ultimately neglect proper sun protection. “When people use really high SPF products, they tend not to reapply, they tend to stay out in the sun much longer, and they don’t use other protective modalities such as clothing and hats,” he says. Regardless of any increase in protection that a high SPF may or may not offer, one thing is certain: It doesn’t give your body a free pass from sunburns, aging, or cancers, and it doesn’t protect you from those things for any greater length of time than the lower SPF options. Both Dr. Wang and Dr. Gohara emphasized that, no matter what the SPF, it’s crucial to reapply your sunscreen every two hours.

　　事實(shí)上，Wang博士也指出，當(dāng)人們選擇高SPF值的防曬霜時(shí)，他們就覺得很有安全感，從而忽略了必要的防曬措施。“當(dāng)使用高SPF防曬產(chǎn)品時(shí)，人們一般就不會(huì)補(bǔ)擦，而且經(jīng)常在太陽底下待很長時(shí)間，也不采取其他的防曬措施，諸如穿防曬服，戴防曬帽等。”不論高SPF的防曬霜是否在隔絕紫外線能力上有所加強(qiáng)，有一件事是肯定的，即它們無法完全避免曬傷，皮膚老化或者皮膚癌。而且它們也不會(huì)比其他低SPF值得防曬霜防曬效果更持久。Wang博士和Gohara博士都強(qiáng)調(diào)，無論防曬霜的SPF值是多少，一定要每隔兩小時(shí)補(bǔ)擦。

　　Which brings us to what is potentially the most important factor of the SPF conversation: Human error. True, an SPF 30 sunscreen technically blocks about 95% of UVB rays, but that’s only when it’s used correctly — and it’s usually not. “Most people don’t use enough sunscreen, so the real SPF protection they’re getting is about one third of the labeled SPF,” Dr. Wang says. “So, if you have a product that says [SPF] 60, you’re really getting an SPF of maybe 20 or 30.” Though there’s plenty of available information on how to properly apply sunscreen — including instructions on the bottles themselves — most of us simply don’t lather on as much product as is used in testing and labeling SPFs. On top of that, we miss spots, we forget to reapply, we go in the water too soon, and we don’t compensate for these errors with supplemental protection.

　　這就引申出使用防曬霜一個(gè)最關(guān)鍵的方面：人為失誤。的確，SPF值為30的防曬霜可以隔絕93％的紫外線，但前提是人們的使用方法必須正確。可是通常人不會(huì)正確使用防曬霜。Wang博士指出：“大多數(shù)人防曬霜的用量不夠，導(dǎo)致使用的防曬霜防曬效果只有實(shí)際SPF值得三分之一左右。因此當(dāng)使用SPF值為60的防曬霜時(shí)，真正有用的SPF值僅僅為20或30。”雖然有很多教大家如何正確使用防曬霜的教程，包括防曬霜瓶子上也有，大多數(shù)人的涂抹量還是達(dá)不到SPF貼標(biāo)檢測過程的用量。除此之外，我們總是會(huì)漏涂，忘記補(bǔ)涂，游泳時(shí)很快跳下水，而且不知道使用別的防護(hù)措施來彌補(bǔ)這些過失。

　　So what does this all mean for your next trip down the sunscreen aisle? It boils down to this: The most important thing is to use a broad-spectrum sunscreen of at least SPF 30 — and to use it often and properly. But, given the fact that none of us is perfect (and certainly not when it comes to applying sunscreen), it just may be worth it to bump that SPF up a notch or two to help make up for that inevitable human error. Just remember that when you do, you should put higher SPF product in your shopping cart. From there on out, it’s (vigilant and careful sunscreen) business as usual.

　　所以這些對(duì)你下次涂抹防曬霜有什么啟示呢？歸根結(jié)底：最重要的是使用廣譜防曬霜（SPF值大于等于30），并且要學(xué)會(huì)合理且頻繁的使用。但是，人無完人（尤其是談到使用防曬霜時(shí)），我們不妨每次多用一點(diǎn)點(diǎn)來彌補(bǔ)那些人為失誤。記住盡可能購買高SPF值的防曬霜，這以后就是正常的防曬工作了。