Are higher SPF sunscreens better? How to pick the right protection

Various sunscreen products are seen in Washington, Wednesday, May 26, 2010. (AP / Evan Vucci)

You’d think that with all that Canadians hear about the risks of sunburns and tanning, we’d be doing whatever we can to protect our skin.

But a recent survey -- commissioned by the Aveeno and Neutrogena sunscreen brands -- found that one in four Canadians do not regularly use sunscreen, while one in three don’t see tanning as risky.

That might help explain why more than 81,000 Canadians will be diagnosed with skin cancer this year, including about 6,000 who will be diagnosed with the most deadly form, melanoma.

While most Canadians use sunscreen, it can be easy to be confused by the array of choices on store shelves. One of the biggest sources of confusion is Sun Protection Factor, or SPF.

A common assumption is sunscreens with an SPF 60 will allow you to stay out in the sun twice as long as an SPF 30.In fact, a sunscreen’s ability to block ultraviolet radiation begins to top out after a certain level. SPF 15 sunscreens block about 93 per cent of UVB rays, the Canadian Cancer Society notes. SPF 30 sunscreens meanwhile block out only slightly more: about 97 per cent of UVB rays. So not twice as effective at all.

Some dermatologists think sunscreens really shouldn’t be allowed to promise an SPF higher than 50.

"The high SPF numbers are just a gimmick," Marianne Berwick, a professor of epidemiology at the University of New Mexico, recently told The Associated Press.

The U.S. FDA is working on setting a limit to SPF promises on sunscreen labels, but for now, the Canadian Dermatology Association advises Canadians to aim for an SPF of at least 30.

Even a sunscreen with high SPF may not do much if Canadians don’t put enough on, says Toronto-based dermatologist Dr. Paul Cohen.

“The issue is when people apply sunscreen, they don’t apply enough,” Cohen told CTV News Channel this week. “When (manufacturers) measure a sunscreen’s SPF value, they use quite a lot. You need to use about a shot glass full to cover yourself.”

Cohen also says the average bottle of sunscreen shouldn’t last you all summer; it should last about a week.

“So you need to apply it often and you need to apply it repeatedly, especially after swimming or sweating,” he says.

“Even waterproof sunscreen -- now we can call it water-resistant – loses its efficacy after 80 minutes and needs to be reapplied.”

Concerns about spray sunscreen

In recent years, spray sunscreens have become hugely popular because they are quick and easy to apply. But some doctors worry about sprays.

Respirologist Dr. Matthew Stanbrook, of Toronto Western Hospital, has concerns about spray sunscreen, especially for children.

He notes many contain oxybenzone, a chemical that absorbs ultraviolet light. While Health Canada and the American Academy of Dermatology says the chemical is safe for the skin, there are concerns that breathing it into the lungs might not be safe for children, because the chemical can act as a synthetic estrogen.

“So there are concerns about breathing those in regularly, especially in developing children, where you can imagine that repeated exposure to synthetic estrogen and testosterone might have some worrisome effects,” he recently told CTV Toronto.

Spray sunscreens also contain particulate matter such as zinc oxide and titanium oxide in their aerosolized spray, he says.

“We know that exposure to fumes or dusts from these types of substances in industrial settings can be associated with some lung diseases,” he says. And he says an aerosol is more likely to release particles that are the right size to be breathed into the lungs.

Stanbrook says the potential problems of breathing in sunscreen have not been studied enough to understand if there is a harmful effect. But he says it’s best to avoid using them with small children.

As well, never spray them directly onto the face; instead, spray the product into your hands and wipe onto the face, he advises.

Finally, there’s one further warning about spray sunscreens: they could be a fire hazard

Last year, a Massachusetts man suffered second-degree burns on his chest, and back after he applied a spray sunscreen before walking over to his barbecue.

The sunscreen hadn’t fully absorbed into his skin, and the propellants in the spray’s vapour trail ignited, causing flames to shoot up his arm and spread over his chest and neck. So be sure to stay away from open flames while using spray sunscreen and rub it in well.