Fact check: Sunscreen protects against cancer, doesn't cause it, experts say

Dezimey Kum, USA TODAY
·5 min read

The claim: The sun does not cause cancer, chemicals in sunscreen do

As heat waves continue to blast the country, Americans have been descending on beaches in large numbers, and many go armed with bottles of sunscreen.

But the practice of slathering on a layer of sun protection is controversial among some on social media even though medical experts routinely recommend wearing sunscreen to ward off skin cancer.

One claim includes the assertion that cancer is actually caused by sunscreen – not the sun.

"With summer around the corner, this is your reminder that the (sun) does not cause cancer," the May 11 Facebook post reads. "Chemicals in sunscreen baking into your skin does."

The post accumulated nearly 300 interactions in a month. Similar claims have also emerged on Facebook.

But sunscreen does not cause cancer. Experts say ultraviolet radiation in sunlight is a primary cause of skin cancer, and sunscreen is an effective method for blocking UV rays and preventing skin cancer.

USA TODAY reached out to the users who shared the claim for comment.

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The sun causes cancer based on UV rays

Research has long established that UV radiation from the sun is the main driver of skin cancer. UV light induces mutations in skin cells that develop into skin cancer.

"The mechanisms of this cancer-causing exposure include UV rays inducing DNA damage," said Dr. Timothy R. Rebbeck, a professor of cancer prevention at the Harvard T.H. Chan School of Public Health. "The relationships are complicated by skin pigmentation that naturally blocks harmful UV rays."

As a 2017 study published in the journal Cell Stem Cell found, UV rays stimulate melanoma tumor growth after exceeding a mutation threshold, which varies based on people's natural levels of melanin, the skin's pigmentation.

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Sunscreen protects against harmful UV rays

When applied appropriately, sunscreen prevents skin cancer by blocking UV rays.

"Sunscreen is effective in blocking damaging UV rays," Rebbeck said. "The efficacy of this blockage is reflected in the SPF rating, with higher SPF suggesting that it is safer to stay in the sun longer."

The concerns about sunscreen have been around for years, and they arose most recently after several sunscreen products were voluntarily recalled, according to Dr. Michael Girardi, a professor and vice chair of dermatology at the Yale School of Medicine. Both sunscreen and after-sun care products were found to have traces of benzene, a chemical sometimes used during the manufacturing process that is known to cause cancer and is associated with leukemia.

Still, health experts are not even convinced that the sunscreen products – which companies voluntarily took off the market – posed a danger.

"Whether such contaminants are at high enough levels to put regular and frequent users of sunscreens at risk of developing leukemia is not clear, but should be studied carefully," Girardi said.

Long-term observational studies have revealed using sunscreen is associated with a reduced risk of developing cancer-causing cells.

A 2018 study published in the journal JAMA Dermatology found that sunscreen is an effective form of UV protection that lowers the risk of developing melanoma as a young adult. Sunscreen use lowered the risk of melanoma in individuals aged 18 to 40, with frequent sunscreen users having a 35% to 40% lower risk than non-users.

Another study published in 2020 in the journal BMJ Open found that the use of sunscreen can protect the skin against melanoma. According to the study, frequent sunscreen use can prevent "substantial numbers of new skin tumors, melanoma deaths and save healthcare costs the researchers wrote."

Rebbeck said there is not sufficient evidence to say that sunscreen is generally harmful to the skin.

Healthline reported in 2021 there is "no evidence that any of the ingredients in sunscreen raise your risk of cancer."

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Our rating: False

Based on our research, we rate FALSE the claim that the sun does not cause cancer, but chemicals in sunscreen do. Sunscreen helps prevent skin cancer by blocking UV rays. While additional research is needed into ingredients that leached into some sunblock in manufacturing recently, experts say the safety and effectiveness of sunblock has been repeatedly demonstrated in studies.

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This article originally appeared on USA TODAY: Fact check: Evidence shows sunscreen is safe and effective