Any dermatologist will tell you that most of the wrinkles and age spots we develop through the years can be blamed on sun exposure, but can we actually look younger by regularly using sunscreen? That’s always been assumed but never tested in a rigorous clinical trial—until now.

In an Australian study involving 903 adults under age 55, researchers randomly selected volunteers to either apply sunscreen daily to exposed areas like their face, hands, and neck or to use it only when they thought they needed it. After 4.5 years, they found that the group that slathered on sunscreen daily experienced 24 percent less skin aging—based on the texture of the skin on the backs of their hands—compared to those who only rubbed on sunscreen occasionally, according to the findings published Monday in the Annals of Internal Medicine.

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Study volunteers were provided with a broad-spectrum sunscreen with an SPF (sun protection factor) of 15.

“To our knowledge, whether sunscreen protects humans against visible...skin aging has not been previously tested,” wrote the study authors from the University of Queensland. “We conclude that regular sunscreen use by young and middle age adults younger than 55 can retard skin aging.”

For adequate protection, the American Academy of Dermatology recommends applying an ounce of sunscreen at a time—enough to fill a shot glass—to cover all the exposed areas of your body when you’re wearing typical summer attire like a bathing suit or shorts and sleeveless tops.