Does my makeup protect me from the sun?

Dear, Glamour:

I know wearing sunscreen is important, which is why I chose a foundation with SPF in it. Is this enough to protect my skin from cancer and sun damage? I really want to be safe and keep my skin looking young, but the sunscreens I've tried to wear under my makeup leave my face feeling greasy and have even caused breakouts.

Sincerely,

Not a Fan of Sunscreen

Dear, Not a Fan:

Kuddos to you for choosing a foundation with SPF in it. Unfortunately, it's not enough to count on your makeup for sun protection. The reason? It's unlikely you're applying enough foundation to get the full benefits of its SPF (sun protection factor).

Take, for example, that to receive maximum protection in a sunscreen, you need to rub at least 1.5 to 2 ounces of the lotion on your skin every time you use it—the equivalent of filling up a shot glass. That measurement also applies to the SPF in your makeup.

As board-certified dermatologist April Farrell, MD, says, "Rather than relying just on your foundation, a better approach is to first put on a daily moisturizer with at least SPF 30 and then use makeup with SPF in it over the moisturizer." And, yes, layering moisturizer and makeup with SPF is necessary year-round, not just in summer months. "You're still out and about in the winter and sun reflects off snow," Dr. Farrell says. "You get more sun when it's cold outside than you realize."

You also can limit the greasy skin and breakouts you mentioned by finding a moisturizer with an SPF that is specifically formulated for the face.

For beach days and other moments when you're spending a lot of time outside and need full-body protection, stick to these sunscreen rules.

Sunscreen rules:

Choose a physical blocker. There are two types of sunscreens: those with physical blockers and others with chemical blockers. Physical blockers, which include minerals like zinc oxide and titanium oxide, work like a shield to deflect sun. Chemical blockers act more like a sponge, absorbing and then disbursing rays. While both offer sun protection, physical blockers work faster and longer than chemical blockers, when applied correctly. They also don't irritate the skin, so they're great for people who have sensitive skin.

Keep babies out of the sun. While physical blockers are safe for almost everyone, tots 6 months or younger should avoid the sun altogether. Once babies reach 6 months old, it's safe to use a sunscreen with physical blockers on them. Until then, make sure infants stay out of the sun and covered. Hats are encouraged.

Reapply often. It's not enough to put sunscreen on in the morning and call it good. Regardless of the SPF you're using, you need to lather up often. "It's important to put on a thick layer of sunscreen and reapply it every 90 minutes to two hours or after you've been swimming or sweating," Dr. Farrell says.

Opt for a lotion with SPF 50 or more, not sprays. While sunscreen sprays might seem more convenient than lotions, they often don't provide as much protection. "I'm not a big fan of the sprays," Dr. Farrell says. "They go on too thin and uneven. Half ends up in the air and on the ground. You just don't get thick enough coverage." Speaking of enough protection: Choosing a sunscreen with SPF 50 or more will help ensure you're staying as safe as possible.

Glamour tip: If sunscreen tends to sting your eyes, choose a sunscreen for your face in the form of a stick rather than a lotion or spray. (Yep, they look like glue sticks from your third-grade art class.) Sunscreen sticks are less likely to run when you swim or sweat.