The sunscreen screening site, put together by the Environmental Working Group, gives detailed information about all the products and groups them by the types of harmful rays they're meant to protect against.
The EWG has cautioned the public in the past about health concerns involving certain cosmetics and seafood.
It unveiled the sunscreens site on Early Show Tuesday.
Jane Houlihan, the EWG's vice president of research, supervised the site's construction.
She explained to co-anchor Julie Chen that there are two things people need from sunscreens more than anything else. One is broad spectrum coverage, from both UVA and UVB rays. The other is stability in sunlight.
It's important to note, she said, that SPF numbers on sunscreen packages only cover UVB, the type of ray most responsible for burns.
UVA is far less responsible for burning, but still can raise skin cancer risk, and only one sunscreen in five has effective UVA protection, Houlihan pointed out. There is no number that quantifies UVA protection, which depends on several factors. There are ingredients that protect well against UVA, but sunlight can break them down and make them ineffective if they're not formulated well.
Also, when sunscreen ingredients break down, they can penetrate the skin and trigger allergies. The ingredients are actually designed to break down; that's part of the function of absorbing energy and keeping it out of the skin. But some break down more quickly and easily than others.
The two ingredients Houlihan likes most are zinc and titanium, which don't break down in sunlight as others do, and offer longer lasting protection as a result. They also work by reflecting sunlight, rather than absorbing it.
Consumers should look for both SPF numbers and zinc and titanium when buying suncreens, Houlihan observed. High SPF protects best against UVB. Zinc and titanium offer maximum UVA protection.
Several ingredients are far less desirable although, depending on how they're blended and what else the products contain, they're not automatically undesirable. They are avobenzone, oxybenzone and padimate O, a relative of PABA, which has come into disrepute in recent years.
The Web site's rankings show that a sunscreen being popular doesn't necessarily mean it's among the best. Coppertone, for instance, has some items in higher categories, but also makes a number whose stability could be better.
One problem with sunscreens is that this country is behind the curve, Houlihan notes. European regulators have approved several effective products that the Food and Drug Administration hasn't gotten around to testing. So, Americans are limited in our choices.
Even if your sunscreen is good, Houlihan stressed that you still need to take all the standard precautions against the sun, such as staying out of the sun during peak hours, wearing protective clothing and hats, and reapplying sunscreen often.