And now the Food and Drug Administration is cracking down on what companies can claim on their sunscreen labels.
"The companies have to tell you how long the protection lasts, so you'll see 40 minutes or 80 minutes on the label," said Courtenay Smith of Reader's Digest.
That's how often you should re-apply.
And there are more new rules.
"Starting in June, companies will no longer be able to say that they lower your risk of skin cancer or aging unless they have an SPF of 15 or higher," said Smith.
Reader's Digest recommends wearing an SPF of 30 or higher as often as possible. For sensitive skin, Smith suggests fragrance-free or dye-free lotions and sprays. Also, look for mineral ingredients like titanium dioxide, which are less irritating to the skin. La Roche-Posay and Aveeno carry mineral sunblock lotions.
But whichever product you choose, beware of the term "waterproof".
"Some say waterproof, that is a myth," said Smith. "The FDA does not recognize that term and there's no such thing as a waterproof or sweat-proof sunscreen."