Think you know what sunscreen is and what it’s supposed to do? If you’re like most people, you probably don’t. A new study finds the majority of consumers don’t completely understand the information on a sunscreen label.
Northwestern University researchers surveyed 114 patients at a dermatology clinic to determine what they knew and understood about sunscreen.
Researchers gave the patients a bottle of sunscreen and asked them to read the label. Then the researchers asked the patients about the definition of sun protection factor (SPF), whether it protects against early aging, and how well the patients thought the sunscreen would protect them against skin cancer.
The researchers found that just 43 percent of those surveyed completely understood what SPF is and what it does.
Most of the people surveyed correctly identified higher SPF values as being directly correlated with increased protection against sunburn and skin cancer. But only 29 percent understood that the SPF number doesn’t indicate protection against aging.
To understand how sunscreen works, it helps to know more about the sun’s rays. Sunlight contains two types of ultraviolet (UV) light that can harm your skin: UV-A and UV-B, says dermatologist Melissa Piliang, MD.
“While UV-B causes sunburn, it’s the UV-A rays that cause aging of the skin, and both types cause skin cancer,” Dr. Piliang says.
The SPF number tells you only how well the sunscreen deflects UV-B rays. Manufacturers calculate SPF based on how long it takes for skin to sunburn with the sunscreen applied compared with skin without sunscreen. So SPF is not going to tell you how much protection the sunscreen offers against skin aging, Dr. Piliang says.
The best sunscreen is a broad spectrum sunscreen, which offers protection from both types of UV light, Dr. Piliang says.
“What you need for the best protection against aging – and skin cancer — is a broad spectrum sunscreen, which is designed to protect you from both type of ultraviolet rays,” Dr. Piliang says.
Researchers say some changes may be in store for sunscreen labels to help us better understand the information.
Dr. Piliang says you should make sure your sunscreen is a broad spectrum, with an SPF of 30 to 50 and is water-resistant or water-proof.
“The brand of sunscreen you choose is not as important as how you use it,“ Dr. Piliang says.
Apply generous amounts of sunscreen – about the amount that would fill a shot glass — to dry skin 30 minutes before you go outdoors, Dr. Piliang says.
“Don’t forget to put sunscreen on your face, ears, hands, arms and lips, and if you don’t have much hair on the top of your head, apply sunscreen to that area or wear a hat,” she says.
Reapply the sunscreen every two hours — and immediately after swimming or if you are sweating heavily. And be sure to use sunscreen even when it’s overcast, Dr. Piliang says, because UV rays can pass through clouds.