As sunscreen ages, its sun-protection ingredients degrade, reducing its effectiveness.

防晒霜老化后，防晒成分的纯度会降低，导致防晒效果变差。

Keeping a fresh bottle on hand, and using it every time you’re out in the sun, will keep you from getting sunburned and also help prevent skin cancer, the most common cancer of all.

准备一瓶保质期新鲜的防晒霜，每次出门有日晒时拿来用，能够防止晒伤，还能预防最常见的癌症皮肤癌。

If your sunblock doesn’t have an expiration¹ date on the bottle for some reason, though, keep Dr. Shari Lipner’s advice in mind.

如果你的防晒霜不知为什么没有保质期，那就谨记莎莉?李普诺医生的建议。

“Sunscreens are designed to last for three years,” says the assistant professor of dermatology at Cornell University’s Weill graduate school of medicine.

“防晒霜一般都有三年的保质期，” 康奈尔大学威尔医学院皮肤医学科副教授莎莉?李普诺医生指出。

“If your bottle does not have a date printed on it, write the date that you purchased it [on the bottle] and make sure to discard after three years.”

“如果防晒霜瓶子上没有印有保质期，那么就在这瓶防晒霜上写上购买日期，确保满三年后不再使用。”

She also notes that storing your sunscreen in a hot car can degrade key ingredients, causing it to become less effective. “If the consistency² seems off — runny or grainy,” she advises, “discard and buy a new sunscreen.”

她还指出把防晒霜置于温度高的车内会破坏防晒主要成分，从而降低防晒效果。她建议，“如果防晒霜的稠度有变化——变稀或出现颗粒，那就扔掉再买一支新的。”

And if you do end up with a sunburn this summer, don’t freak out. There are ways to treat it and reduce its more insufferable side effects.

如果这个夏天你被晒伤了，那也别慌张，这里有一些方法能够减轻痛苦难忍的副作用。

First, get out of the sun as soon as possible. Then, take a cool shower or bath, and apply cool compresses to any burned or red areas for 10-15 minutes, four times a day.

首先赶紧躲避日晒，然后冲一个冷水澡或洗冷水浴，紧接着在晒伤或晒红处进行10至15分钟的冷敷，每天四次。

“Aloe vera and moisturizer are soothing³ and will help the skin heal faster,” she says. And you can take ibuprofen to help with swelling⁴. “If it blisters⁵, never pop the blisters. Let them heal on their own to avoid infections。”

“涂抹芦荟和润肤膏能缓解疼痛，帮助皮肤尽快愈合，”她说。另外，可以服用布洛芬抗肿胀。“如果起了水泡，千万不要挤破，让它们自己慢慢愈合以免感染。”