SPF 101: What it is, how it works and why we need it
For Canadians, Victoria Day weekend is the kickoff to summer. Cottages and pools are opened, long-range weekend plans are made, and fridges and coolers get stocked. But the one thing Canadians consistently fail to do is reach for the SPF.
According to a recent report from Statistics Canada, only 45 per cent of adults wear sunscreen on their faces and 38 per cent report applying it to their bodies. There’s a gender bias, too — more women than men wear sunscreen regularly.
Now for the even scarier facts: skin cancer is the most common cancer in the world, and melanoma (the deadliest form of skin cancer) is the seventh most common cancer in Canada. Furthermore, diagnosis rates in the country have more than tripled over the last 30 years, according to the Melanoma Network of Canada.
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“There have been 7,000 new cases of melanoma diagnosed in Canada so far in 2017, and it’s estimated that there will be 80,000 cases of skin cancer diagnosed this year,” says Annette Cyr, founder and chair of the Melanoma Network. “Of the 7,000 melanoma cases, 2,000 likely won’t survive.”
To break it down, there are three types of skin cancer: basal cell carcinoma, which is the most treatable, although removal of cells can cause disfigurement and it can spread continuously; squamous cell carcinoma, which is more aggressive; and melanoma, which is a rarer form of the disease but can easily metastasize and is responsible for 80 per cent of all skin cancer deaths.
There are a number of precautions people can take, from wearing protective clothing and hats to avoiding the sun during the peak hours of 11 a.m. to 3 p.m. (especially the dangerous noon to 2 p.m. slot). But the most common, user-friendly and frankly, easiest thing to incorporate into your lifestyle, is to slap on SPF.
What is SPF?
An acronym that stands for sun protection factor, SPF is a measure of how much protection a sunscreen can afford. The going philosophy on SPF used to involve a mix of math skills and self awareness. For example, if it takes 20 minutes of unprotected exposure to the sun for your skin to redden, an SPF of 15 would theoretically provide you with 15 times more protection, which equals about five hours.
But the Skin Cancer Foundation points out that this is a flawed model. For one thing, experts stress that sunscreen should be reapplied every two hours regardless of the SPF level because no sunscreen has proven longevity beyond that time frame. Also, reddening of the skin is a result of exposure to UVB rays, but a sunburn does nothing to indicate how much UVA exposure you’ve had. (UVA rays cause skin aging, while UVB causes skin to burn. Both are associated with skin cancer and both are a year-round concern.)
For this reason, in 2012, Health Canada announced that all sunscreens sold in Canada would need to offer broad spectrum protection, meaning that it would block both UVA and UVB rays. This is especially significant as “growing research has shown that UVA rays have the ability to penetrate more deeply and cause genetic damage to cells,” Cyr says.
And while UV rays are positioned as a danger that’s exclusive to the outdoors, studies have shown that even if you’re behind glass, you can be affected by them.
“UVB rays do not penetrate glass to a significant degree, but UVA rays do,” says Dr. Channy Muhn, dermatologist and co-founder of Dermetics dermatology clinic in Burlington, Ont. “That’s why protecting yourself daily, not just when you’re on the beach, is important.”
In fact, a 2016 study published in JAMA Ophthalmology found that car side windows only blocked an average of 71 per cent of UVA rays, which the study authors said could potentially explain the increased rates in cataracts and (as North Americans drive on the left side of the road) left-side facial skin cancers.
How much SPF should I aim for?
Experts across the board say everyone should wear a minimum of SPF 30 daily. Although Dr. Nathan Rosen, dermatologist and co-founder of Dermetics, recommends SPF 45 or higher to his patients.
“Most people don’t apply enough, or often enough, for optimal protection,” he says. “If you’re outdoors, be sure to apply a generous amount 30 minutes before exposure, and reapply every two hours, or immediately after swimming or heavy sweating. For indoor or day-to-day activities where exposure is less intense, once or twice per day is generally sufficient.”
In recent years, cosmetic companies have been raising the SPF claims on their products, sometimes even going as high as SPF 100. But experts caution against these claims.
“SPF 30 blocks 97 per cent of UVB; an SPF of 50 blocks 98 per cent. But SPF 100 isn’t twice as effective as SPF 50,” Muhn says. “High SPFs can make consumers feel more protected than they really are, which may cause them to stay in the sun longer than they should or to reapply less often.”
The solution: Wear a minimum of SPF 30 and reapply at least every two hours if you’re out in the sun.
How much product should I apply?
For adequate head-to-toe protection, you should apply a shot glass-worth of sunscreen. But unless you’re knocking back tequila poppers poolside, it can be difficult to know you’re applying enough.
Don’t worry, though, because you’re definitely not overdoing it.
According to the American Academy of Dermatology, most people only apply 25 to 50 per cent of the recommended amount of sunscreen. Your body requires about two tablespoons of product, while your face needs a nickle-sized dollop. If you’re using a spray-on sunscreen, experts recommend applying enough so that you see a sheen all over your body or spraying it in your hands and rubbing it on manually.
Should I use a physical or a chemical sunscreen?
Both have proven to offer effective forms of sun protection. It comes down to personal preference.
“Chemical sunscreens absorb and neutralize UV rays, whereas physical blocks use minerals like zinc and titanium dioxide to reflect UV rays and prevent them from being absorbed by the skin,” Rosen says. “One isn’t necessarily better than the other, although physical blocks can be less irritating for sensitive skin.”
In either case, he stresses to always check the expiration date on your sunscreen. Never use one that’s past its due date and discard any leftover product at the end of the season.
But I heard that most sunscreens don’t work
A recent Consumer Reports analysis conducted in the U.S. looked at 58 sunscreens and found that 20 of them offered less than half the SPF written on the label. And while the report is garnering a fair share of media attention, experts caution that this isn’t the first time claims of this nature have been made.
“This isn’t new,” Cyr says. “But the missing component of this study is that people generally don’t use sunscreen correctly: they apply it too thinly and not frequently enough.”
Dr. Beth Jonas, chief scientist of the Personal Care Products Council said in a statement: “It appears their testing methods are not consistent with those used by the U.S. Food & Drug Administration. Therefore, their testing methods are not the same as those required of product manufacturers to assign the SPF designation.”
I’ve never worn SPF, the way I see it, the damage is already done
The experts stress that it’s never too late (or too early) to make SPF a regular part of your daily routine. They’re also eager to dispel any misgivings about sunscreen texture.
“Sunscreens have come a long way from the thick, white, goopy products many people remember. New formulations are lightweight, transparent and feel more like makeup or moisturizer,” Muhn says.
He also points out that if caught early enough, skin cancer is highly treatable, and although premature aging caused by sun damage can’t be reversed, there are cosmetic options to improve skin texture, like laser resurfacing.
But at the end of the day, there’s only one takeaway: “Protection is always better than correction.”
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