the sunscreen guide...that will change your life

From the amount to use (it may be more than you think) to the differences between mineral and chemical SPFs, our handbook will help you stay safe and have fun in the sun.

- Erica Metzger

If you could buy only one skincare product for the rest of your life, it should be face sunscreen.

Along with helping you steer clear of painful sunburns, it's proven to fend off skin cancer, one of the most diagnosed (and preventable) cancers in the U.S.

Also, sunscreen protects against UV damage, which is responsible for 80 percent of visible face aging.

Sunscreen is so important that dermatologists want you to stash a tube somewhere conspicuous so that using it becomes habit. (Keeping sunscreen next to your toothpaste, for example, increased usage, one study found.) "Look for an SPF of 30 and apply it to your face, ears, neck, and hands every morning-rain or shine, winter or summer-and reapply again after two hours, even if you're just sitting near a window inside or walking around casually outdoors," says Shari Marchbein, MD, an assistant professor of clinical dermatology at New York University School of Medicine.

But as critical as sunscreen is, it's not foolproof. You must use it correctly to enjoy its protective benefits which means knowing how much to apply. WH tapped top dermatologists to create a helpful guide that breaks down what sunscreen is, how it works, and, most important, how much you should really be slathering on every day.

Better-Skin Basics

To start, it helps to understand how these products work. Sunscreens use specific FDA-approved ingredients to shield skin from the harmful effects of ultraviolet (UV) light generated by the sun. UV radiation is responsible for 80 to 90 percent of skin cancers, and there are two types. UVB is primarily responsible for burns, while UVA is more associated with aging. "But we now know that both contribute to skin cancer and aging," says Anthony Rossi, MD, a dermatologist at Memorial Sloan Kettering Cancer Center who specializes in Mohs micrographic surgery-a technique that removes skin cancer while preserving healthy tissue.