Here's Why You Need Sun Protection All Year Long

As for how much you should apply, Michael Swann, MD, dermatologist in Springfield, Missouri, points out that most people don't apply nearly enough sunscreen to provide the SPF protection on the label, so more is always better. "Studies show people put about one-third of the sunscreen necessary to give them the protection listed on the label (SPF 45), which results in them getting much less protection than they expect they should get," he says.

In the summer, you usually need about a shot glass worth of sunscreen per side of your body, says Patel. "In the cooler months with more clothing on for more protection, it is important to apply a quarter size amount to your face, hands and any other sun-exposed areas," she says. Since so many people don't apply enough sunscreen, Sarkar usually recommends applying one layer and then a second layer.

And yes, you should still apply sunscreen even if you spend the majority of your time indoors. "With respect to windows, glass only filters shorter wavelength UVB rays," says Batra. "However, UVA rays, which have a longer wavelength and penetrate more deeply, can still pass through glass." That's why Batra says people who spend a lot of time in the car often have more signs of sun damage on the skin on their window side. Patel adds that sunscreen will also help protect your skin from damaging blue light radiation from computers and devices.

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