UVA versus UVB Rays - Why you need to know the difference

Most sunscreens fare well when it comes to blocking UVB rays – the most superficially penetrating rays, responsible for giving us a suntan (or burn). UVB rays also contribute to skin cancer and aging.

UVB protection is measured by Sun Protection Factor (SPF). "If you have a sunscreen with an SPF15, you can stay out in the sun for 15 times longer than you could without that sunscreen and not get a sun burn," says Dr. Paul Cohen, a Toronto-based dermatologist.

But SPF doesn't protect your or your kids from UVA rays.

"UVA rays penetrate deeper than UVB," says Dr. Cohen. Although they don't physically tan or burn your skin, they are the primary rays responsible for premature aging and skin cancer.

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