Health

Sunscreen helps prevent, not cause, cancer — despite what you might have heard

Experts are warning Canadians not to heed misinformation spread online that sunscreen can cause cancer, stressing that proper use of the right lotions or sprays is, in fact, one of the best ways to prevent potentially deadly ailments like melanoma. 

Quebec’s Order of Chemists warned last week against what it called a worrying trend circulating on social networks where some influencers spread false and misleading information about sunscreen, claiming that its ingredients are harmful to the skin and can cause cancer. The group said the assertions, devoid of scientific basis, can endanger public health.

One such influencer on TikTok recently warned their 570,000 followers to not use any sunscreen whose ingredients have “any funny words other than zinc.”

Julia Carroll, a dermatologist in Toronto, says much of the misinformation fails to look at the medical literature as a whole on sunscreen ingredients, which points to their safety.

“I’m a board-certified dermatologist,” Carroll said. “I have 20 plus years of training and education and we dedicate ourselves to looking after the health of our patients’ skin. And one person on TikTok that just happens to have a lot of followers can sway someone’s opinion. It’s really frustrating for all of us.”

She says some influencers overlook how it’s the dose that makes the poison. Too much of almost any substance can kill you while, in small amounts, even toxic substances like botulinum toxin can be safe.

Some influencers claim certain sunscreen ingredients cause cancer or other ailments. Others say sunshine is the best way to get vitamin D.

According to the Canadian Cancer Society, about 65 per cent of melanoma cases are due to ultra-violet (UV) radiation, the main source of which is the sun. Melanoma is a form of skin cancer that starts in the skin’s pigment-producing cells or melanocytes.

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The authors of a report on projected estimates of cancer in Canada for 2024 noted the incidence of melanoma continues to increase for both males and females, although mortality has remained largely stable.

Cheryl Peters, a senior scientist at the B.C. Centre for Disease Control and B.C. Cancer, attributed the rise in melanoma to a combination of factors. People may expose more skin to stay cool during hotter summers with climate change, she said. Canada’s aging population also matters since the risk of most cancers increases the older you get.

Check UV index

In Canada, weather forecasts and apps include information on the UV index. 

“Once you start to hit that UV index of 3, you really want to be wearing your sunscreen and reapplying it regularly,” Peters said on CBC Radio’s Just Asking

The first layer of defence is to reduce time in the sun during its peak rays of 10 a.m. to 3 p.m., by seeking shade and covering up as much of your skin as you can with clothing that is made from tightly woven fabric or clothes labelled with a UPF (UV protection factor), a wide-brimmed hat and sunglasses.

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It’s true that a bit of sun exposure does help the body produce vitamin D, which is important for our bones and other health aspects.

But Carroll says people shouldn’t rely on it to get their vitamin D. “If vitamin D is really important to you, the easiest way and most consistent way to get it is through a supplement,” she said. 

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Sunscreen explained

Sunscreen comes in two major types, mineral and chemical.

Mineral sunscreens contain zinc oxide or titanium dioxide. The mineral flecks create a barrier reflecting UV light before it penetrates the skin. Because mineral sunscreens create a physical block and aren’t absorbed, the formulations can have a white appearance.

Chemical sunscreens come as creams or sprays. The ingredients form a thin protective film that absorbs UV rays and converts them into heat before they penetrate the skin.

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Canadian guidelines recommend making applying sunscreen part of your morning routine and putting on a “generous amount” — one to two teaspoons for the head and neck, and two to three tablespoons for the body of an average-sized adult.

Guidelines laid down by the Canadian Dermatology Association require an SPF rating of at least 30. 

Experts also recommend broad-spectrum sunscreens that protect against both UVA rays, which lead to signs of aging like wrinkles, and UVB rays, which lead to sunburn. 

Chemical sunscreens can lose their efficacy when exposed to extreme heat according to a 2012 study in the journal of the American Academy of Dermatology. You can tell if sunscreen may have been exposed to extreme heat if its components have started to separate. 

So during extreme heat, when temperatures reach 32 C or above, with high humidity, for at least a few days, mineral sunscreens are preferable, says Jacqueline Watchmaker, a dermatologist in Scottsdale, Ariz., and a spokesperson for the academy.

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Otherwise, there isn’t a health-based reason to choose one type of sunscreen over another, says Peters, who researches the prevention of occupational and environmental chronic diseases like cancer.

Chemical sunscreens can cause a skin reaction like a rash in a small number of people, she says. In those cases, shift to a mineral-based product.

Also, chemical sunscreens are suspected of causing harm to some coral reefs so if you’re vacationing in areas with reefs, that’s another time to consider using a mineral-based option, Peters says. 

Lip balms that have a SPF rating are also an important form of protection that a lot of people miss, Peters said.

A woman covers herself with an umbrella during the heat wave in Mexico City in March.
A woman covers herself with an umbrella during the heat wave in Mexico City in March. Clothing and a wide-brimmed hat can help protect skin from the sun’s damaging UV rays. (Quetzalli Nicte-Ha/Reuters)

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