Stocking up on sunscreens as summer approaches? You might want to take a close look at your choices; many sunscreens don't live up to the claims on their labels, a report says.

Of 34 sunscreen products tested by Consumer Reports, almost a third did not live up to the UV protection levels their labels and advertising promised, the organization said.

The products were tested to determine their levels of protection against UVB radiation, which can result in sunburn and which in excessive amounts can lead to skin cancer, and UVA radiation that tans the skin but can increase wrinkling and accelerate aging.

In the tests, participant applied the sunscreens, all of which claimed to be waterproof in addition to providing sun protection, then spent 40 to 80 minutes in a tub of water, depending on how long the products' labels promised they would remain waterproof.

Then the participants were put under ultraviolet light to see if the SPF - "sun protection factor" - the products promised was still performing as it should.

More than 30 percent of the products failed that test, the organization said, with the participants using those products showing considerable redness of the skin the following day.

The wide range of performance, and the fact so many failed to deliver, was unexpected in products so widely sold and used, experts said.

"It's quite surprising, given that sunscreens are highly regulated in both Canada and U.S.," says Dr. Sonya Cook, a dermatologist and lecturer at the University of Toronto.

Another organization, the Environmental Working Group, also released a report saying 80 percent of the sun-protection products it reviewed - including sunscreens, moisturizers and lip balms - offer "inferior sun protection or contain worrisome ingredients like oxybenzone and vitamin A."

Oxybenzone is a chemical that can interfere with the hormone system, and some research has suggested applying vitamin A to the skin can heighten, rather than reduce, sun sensitivity.

Another problem is that many people, when summer starts, grab the sunscreen that's been sitting in the cabinet under the bathroom sink for an unknown length of time.

Not a good idea, says Cook, who recommends checking the expiration date printed on the label before using it.

Can't find a date? Toss it, she suggests.

"I think it's a good idea every year, do a little spring cleaning of your sunscreens, and toss out the ones from last year and start fresh," she says.

She recommends using products that list an SPF of at least 30 and promise protection from both UVA and UVB rays.

Lotions and creams normally offer better, more effective coverage than sprays or liquids, she adds. And in addition to sunscreen, she suggests using other protective measures - wearing sunglasses, hats and sun-protective clothing and avoiding exposure during the peak hours of 11 a.m. to 4 p.m. If you can't avoid the peak times, slather on the lotion.

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