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Sunscreen Myths and Facts

Contributor: Charles Yoon, MD, PhD
6 minute read
A mother puts sunscreen on her child’s face in winter

Skin cancer is the most common cancer in the United States. It affects up to 1 in 5 Americans, according to statistics from the American Academy of Dermatology.

Sun exposure is the single largest preventable risk factor for skin cancer. Yet many Americans don’t exercise necessary precautions to protect their skin.

“Skin cancer is a serious, potentially deadly cancer,” says Charles Yoon, MD, PhD, a surgical oncologist at Brigham and Women’s Hospital. “Many types of skin cancer are just as aggressive as colorectal, breast, or lung cancer.”

Debunking sunscreen myths

Despite the well-documented benefits of sunscreen to prevent skin cancer, like those reported in the Canadian Medical Association Journal, some people still question its importance. In part, this is because of several common misconceptions:

Myth: You won’t get sun damage if you reapply sunscreen every few hours.

You’ve likely heard that you should reapply sunscreen every few hours when spending time outside. What many people don’t understand, however, is that sunscreen simply delays how quickly you’ll experience sun damage. Reapplying every few hours isn’t enough to bring your risk to zero.

Dr. Yoon uses the analogy of an oven mitt to explain sunscreen application. Wearing an oven mitt offers an extra layer of protection so that you don’t burn your hand when you pick up a hot pan. However, if you hold the hot pan for an hour, the heat will eventually go through the oven mitt and damage your hand.

Reapplying sunscreen after an hour is like switching out a fresh oven mitt. It may delay the time it takes to burn, but it doesn’t prevent damage entirely. It also doesn’t undo the hour of damage that’s already occurred. For true protection, even with sunscreen, you still need to limit your total time spent in the sun.

Myth: You don’t need to reapply waterproof sunscreen after swimming or sweating.

Apply sunscreen after sweating, like during a long bike ride.

You may think “waterproof” sunscreen means that you can swim or sweat without any risks. However, there’s no such thing as truly waterproof sunscreen according to the Food and Drug Administration (FDA).

Sunscreens marketed as “waterproof” are only water-resistant. They may last longer in the water than other sunscreens, but they still wash off eventually. You need to reapply sunscreen more frequently when you sweat or swim.

Myth: You don’t need sunscreen on a cloudy day or during winter.

Some people think that they won’t get sun damage if they can’t see the sun, such as during a rainy or gray winter day. But clouds generally provide little protection from the sun.

Sun damages your skin because it gives off ultraviolet (UV) radiation, specifically UVA and UVB rays. The UV index rates the intensity of those rays at a given time. Higher UV indexes are associated with a higher risk of burning. A UV index of 6 or 7 is considered a high risk of sun damage.

“Even with cloud cover, the UV index often exceeds 6 or 7,” explains Dr. Yoon. “It would take a hurricane or other significant storm to provide real protection from cloud cover — and you likely wouldn’t want to be outside in that.” 

Myth: Tanning is better than burning.

You may believe that the only sun damage worth worrying about is a severe burn. But, Dr. Yoon says, “Tanning is burning. Both are signs of cellular damage to your skin.”

When you spend time in the sun, your skin cells become damaged. The damage may look like a burn, or it may look like a slight tan. It only takes 15 to 20 minutes for these changes to become irreversible, increasing your risk of skin cancer.

Myth: You don’t need sunscreen if you have darker skin.

It’s important to apply sunscreen even if you have darker skin.

“If we think about how populations evolved, people have different skin tones based on the latitude where they lived,” Dr. Yoon explains. “People who lived closer to the equator, where UV exposure is more intense, have more melanin in their skin.”

Melanin is the natural substance that gives your skin pigment. It helps protect your skin from sun damage.

However, the protection melanin provides is slight. It’s still important to wear sunscreen to avoid skin damage.

Fact: Sunscreen lowers vitamin D production.

It’s true that sunscreen lowers the efficiency of vitamin D production. This is because our bodies make vitamin D through UV exposure. Vitamin D is an important nutrient that helps your body absorb calcium to keep your bones healthy and strong.

Wearing sunscreen or having darker skin causes your body to make vitamin D from sun exposure less efficiently. Luckily, we have vitamin D supplements to compensate for any deficiencies.

Skin cancer is highly treatable when caught early. Our team is nimble in adopting new standards of care because we’re directly involved in generating them.

Charles Yoon, MD, PhD
Surgical Oncologist
Brigham and Women’s Hospital

Skin cancer prevention and treatment

Wearing sunscreen daily is one strategy to lower your risk of skin cancer, including melanoma and squamous cell carcinoma. Additionally, there are many other steps you can take:

  • Avoid sun exposure when the UV index is highest, usually between 10 a.m. and 4 p.m.
  • Choose a sunscreen with an SPF of 50 or higher and remember that it wears off more quickly when you sweat.
  • Limit direct exposure during times of high UV index to 1 hour or less, even when using sunscreen.
  • Talk to your doctor early if you notice any skin changes.
  • Visit a dermatologist annually for skin checks.

“Skin cancer is highly treatable when caught early,” says Dr. Yoon. Patients at Mass General Brigham have access to the latest skin cancer treatments, including through clinical trials. “Our team is nimble in adopting new standards of care because we’re directly involved in generating them.”

Learn more about the signs of skin cancer
Charles Yoon, MD, PhD

Contributor

Charles Yoon, MD, PhD
Surgical Oncologist