If you're not going outside, you don't need sunscreen, right? Wrong. The sun's UVA rays, those responsible for signs of aging, can penetrate through glass. So even when you're snuggled up on the couch watching the snow fall outside, your skin is vulnerable. "Picture that faded picture hanging in your living room. The same thing can happen to your skin," points out Gohara.

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Sorry to be repetitive (actually, we're not sorry because this is important), but once again, using a sunscreen with at least SPF 30 every darn day is the best thing you can do. Make sure it's labeled broad-spectrum, which indicates that it protects from both UVA and UVB rays. Other than that, the formula you pick is a matter of personal preference. We like Exuviance Sheer Daily Protector SPF 50, $42, which is also tinted, a nice option for makeup-free days. Also important: Use at least a nickel-size amount for your entire face to ensure you're getting adequate protection.

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When temps are frigid, you're obviously not going to be outside for hours on end, but even short amounts of time can be problematic. Sun damage is cumulative, so a minute spent grabbing the mail, five minutes popping out of the office to grab coffee, ten minutes walking the dog -- these all add up and can result in serious skin damage.

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Have we made it clear that you need to be wearing sunscreen? You can also protect yourself with clothing, and hey, it keeps you warm, too. A hat is a great way to shield your scalp, gloves to cover your hands, a scarf to hide your neck and chest. Bundle up!

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Aside from the fact that you're exposed to the UVA rays coming in through your office window, there's another sneaky source of damage lurking in your office -- visible light, the kind emitted by lightbulbs. While this is a different type of energy than the sun's rays, it can cause skin damage and worsen melasma, says Gohara.

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