Sunscreen isn't just for pool gatherings and beach outings: Using sunscreen every day could reduce your risk of skin cancer, experts say.

Daily use of at least an SPF 15 sunscreen can lower your risk of melanoma — the deadliest type of skin cancer — by 50%, according to the Skin Cancer Foundation.

If you spend most of your day indoors, SPF 15 should provide adequate protection, but if you spend more time outdoors during the hottest part of the day, you should use a sunscreen with a higher SPF and perhaps one that is also water and sweat-resistant, according to Hackensack Meridian Health, a health care network in New Jersey.

SPF stands for "sun protection factor," and the number indicates how long it takes the sun's UVB rays to redden your skin while wearing the sunscreen, compared with the amount of time without sunscreen.

That means if you use an SPF 30 product as directed, it would take you 30 times longer to burn than if you used no sunscreen.

Your best choice is a broad spectrum sunscreen that protects against both the rays that burn skin and the rays that cause aging and tanning, the health network advised.

A common problem with sunscreen is that people don't apply enough of it. You should completely cover your body, including your ears, scalp, feet and neck, and need to apply lots of sunscreen even on cloudy days, because the sun's UV rays can penetrate clouds, Hackensack Meridian Health explained in a news release.

After you apply the sunscreen, you still need to use other types of protection, such as wide-brimmed hats and UV-blocking sunglasses.

Typically, sunscreen should be reapplied every two hours, especially if you've been swimming or sweating.

It's also important to check the sunscreen's expiration date. Most sunscreens are designed to maintain their original level of protection for up to three years. If you have sunscreen that's expired or more than three years old, throw it out.

Sunscreens that have been exposed to high temperatures or have obvious changes in color or consistency should also be thrown away, the group said.