Sunscreen: What to Look For and How to Use It

Sunscreen helps shield your skin from ultraviolet (UV) rays, the invisible energy from the sun that can lead to skin cancer. Used well, it is a simple and useful part of protecting your skin.

But sunscreen only works if you pick a good one, put on enough, and reapply. And it works best when it is one layer among several — not the only thing standing between you and the sun.

Choose broad-spectrum, SPF 30 or higher, apply plenty, and reapply often.

Two words on the label matter most:

• Broad-spectrum. This means the product protects against both UVA and UVB rays. Both types damage skin, so you want protection from both.
• SPF 30 or higher. SPF, or Sun Protection Factor, measures protection against the UVB rays that cause sunburn. SPF 30 blocks about 97 percent of UVB. Higher numbers add just a little more, and none reach 100 percent.

If you will be swimming or sweating, look for a water resistant label. Note that this only lasts for a set time in the water — usually 40 or 80 minutes — not forever.

Broad-spectrum plus SPF 30 or higher is the everyday standard.

This is where most people fall short. Using too little sunscreen gives you far less protection than the SPF promises.

• FDA says an average-sized adult or child needs at least one ounce — about the amount it takes to fill a shot glass — to cover the face and body.
• Apply 15 minutes before sun exposure.

Do not miss easy-to-forget spots: ears, the back of the neck, the hairline, the tops of feet, and hands. Use an SPF lip balm for your lips.

A thin layer is a weak layer — be generous.

Sunscreen wears off, so one application is not enough for a day outdoors.

• Reapply at least every 2 hours.
• Reapply after swimming, heavy sweating, or toweling off, even with a water-resistant product.

Setting a phone reminder or keeping sunscreen in your bag makes this easier to remember.

Sunscreen is helpful, but it has real limits worth knowing:

• No sunscreen blocks all UV. Some rays still get through.
• People often use it to stay out longer. If sunscreen lets you skip a sunburn but you spend all day in the sun, you may still get a large dose of UV.
• It can be applied unevenly, leaving gaps.

Because of this, experts stress that sunscreen should be used together with shade, clothing, a hat, and sunglasses — not as a reason to skip them.

Sunscreen is a teammate to shade and clothing, not a replacement.

Sunscreen loses strength over time and in high heat. To keep it working:

• Check the expiration date. Sunscreens are made to last at least 3 years, but many print a date.
• Replace bottles that are expired or that have been left in a hot car for long periods.
• Toss any product that has changed color, texture, or smell.

You may see sunscreens described as mineral (with ingredients like zinc oxide or titanium dioxide) or chemical (with ingredients that absorb UV). Both types can protect your skin when they are broad-spectrum and SPF 30 or higher.

• Mineral sunscreens sit on top of the skin and start working right away. They can feel thicker or leave a slight white cast. Many people find them gentle on sensitive skin.
• Chemical sunscreens tend to be lighter and rub in more clearly, which some people prefer for daily use.

The best sunscreen is the one you will actually use, apply well, and reapply. If one type irritates your skin or you simply dislike how it feels, trying the other is reasonable.

Whichever type you choose, applying enough and reapplying matters far more than the category on the label.

Sunscreen can be used on children, and it is an important layer for kids old enough for it. FDA does not recommend sunscreen for infants under six months, and advises keeping them out of the sun during peak hours and using protective clothing instead. Ask your child's care team about the right approach for your baby.

Making sunscreen part of a daily routine — kept by the door, in a bag, or in the car — helps the whole family remember it. Small, steady habits add up to real protection over the years.