The effectiveness of a sunscreen to limit skin exposure is measured by its sun protection factor, or SPF, number. The higher that number, the more protection a product will provide against UVB rays, the ones that cause sunburns.
"People need to use SPF30 and up, and what that reflects is proper UVB protection," says Dr. Anatoli Freiman, chair of Canadian Dermatology Association's sun protection program. "Number 2, the sunscreen should be broad-spectrum, meaning it protects against UVA and UVB as well."
The Canadian Dermatology Association reviews research on various sunscreens and those that meet scientific standards get its stamp of approval. While the CDA logo on the packaging helps consumers know they are choosing an approved product, Freiman acknowledges that many people still don't use sunscreens to get their utmost benefit.
Here is advice for using sunscreen to optimize protection from the sun's harmful rays:
Sunscreen should not be used for babies six months and younger, nor should their delicate skin be exposed to direct sunlight. But older children and adults should be vigilant about using sunscreen, which should be applied at least 15 minutes before going outdoors so it can be absorbed by the skin.
PICK THE CORRECT SPF:
The CDA recommends that consumers use a minimum sunscreen strength of SPF30.
"The question is: is the more SPF, the better?" said Freiman, who is also medical director of the Toronto Dermatology Centre. "And typically, yes, because the higher the SPF, like SPF60, the higher the protection. But the curve sort of plateaus, so with SPF30 you get about 97 per cent protection against UVB rays, and with SPF60, you're getting into about 98.5 coverage.
"So it's incremental increases. That being said, a lot of people underapply sunscreen. They don't apply enough, so in that sense there's actually been some studies that show that getting SPF higher — say SPF70 — can compensate for under-application. So therefore you get a little bit better protection."
While no one becomes immune to sunscreen's effects over time, people have different sensitivities to the sun and may need to use a higher SPF product than others to achieve the protection they need. Fair-skinned people, for instance, can burn more easily than darker-skinned people whose skin contains more melanin, the pigment in skin.
"Some folks who take certain medications can be more sun-sensitive," says Freiman, suggesting they may need to use a product with a reading of SPF60 or higher.
Freiman advises applying the equivalent of about a shot glass-full of sunscreen over the body and about five millilitres (a teaspoon) on the face. "Sometimes people forget obvious places, behind the ears, the lower lip (and) the back of the hands," he says. And don't forget the toes, which are can be exposed in sandals, and the backs of the knees and legs, common sites for melanoma to develop.
Generally, sunscreen should be reapplied every two hours during exposure to the sun (even on seemingly overcast days), but it may be needed more often depending on how hot the weather is and types of activity, he says.
"Nothing is completely waterproof or sweat-proof, so they're more water-resistant," Freiman says of products that are formulated for those engaging in water sports and strenuous, perspiration-producing exercise. Usually, such sunscreens recommend reapplication every 40 to 80 minutes.
"So that needs to be respected because 40 to 80 minutes after, most of the sunscreen is washed off. It depends on the type of the sunscreen, but usually what it means is it needs to be reapplied more frequently than every two hours."
WHEN IN DOUBT, THROW IT OUT:
Because sunscreen can degrade over time, products carry expiration dates, after which bottles should be tossed as their ingredients will no longer offer proper protection.
And while storing sunscreen in a vehicle may make it readily accessible, the heat of summer — or indeed, the cold of winter — can play havoc with products' chemical ingredients, which can lose their power to protect against the sun's rays, says Freiman. "It does reduce effectiveness. It can become photo-unstable ... and disintegrate with time. It probably doesn't go to zero in terms of efficacy, but we don't encourage people to keep it in a heated environment for too long."
IS SUNSCREEN SAFE:
There have been suggestions that the ingredients in sunscreens may be carcinogenic, or cancer-causing, but experts say there is no proof the products carry any risk of harm.
"There's always talk, it's controversial, but basically we do know that the proven studies showing the efficacy of sunscreen with protection against skin cancer clearly outweigh any hypothetical claim," says Freiman. "As scientists, we know that sunscreens work, they make a difference, they prevent skin cancer and that's what we advocate. It's safe and effective."
Statistics released last month by the Canadian Cancer Society show cases of skin cancer — particularly the most deadly kind, melanoma — are on the rise in both women and men. This year, an estimated 6,500 Canadians will be diagnosed with melanoma, and 1,050 will die from the disease.
Besides using sunscreen to prevent skin cancer, experts recommend seeking the shade when outdoors, especially between 10 a.m. and 3 p.m., and covering up with clothing, including a broad-brimmed hat and UV-blocking sunglasses. Skin cancer can occur on eyelids and too much exposure to sunlight can lead to cataracts.
Some manufacturers sell sun-protective clothing that carries an ultraviolet protection factor, or UPF, rating; there are also products that can be thrown in the washer with clothes to make them sun-protective; and special wristbands can tell wearers when they need to reapply sunscreen.
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