The pitch: If SPF 30 is good, SPF 100 must be three times better.
The truth: According to the Skin Cancer Foundation, “SPF 15 blocks approximately 93 percent of all incoming UVB rays. SPF 30 blocks 97 percent; and SPF 50 blocks 98 percent.” Think that’s confusing? You’re not alone. Consumers are so befuddled by the (often meaningless) claims sunscreen makers use that the FDA is issuing a whole new set of rules to try to clear things up. What’s more, SPF only measures one kind of harmful ultraviolet ray, and all sunscreens need to be reapplied every couple of hours.
The exception: You’re very fair-skinned or have a history of skin cancer.