The U.S. Food and Drug Administration regulates both cosmetics and drugs, but they’re not the same thing. The distinction is that drugs affect the structure of your body or the way it works, and cosmetics just make you look nicer. It’s the difference between a tube of mascara and a prescription of Latisse. Try telling that to Lancôme, though. The FDA happened to stop by the company’s website one day, and noticed that the company makes some claims that make their products sound less like cosmetics, and more like drugs.
The difference in UVB protection between an SPF 100 and SPF 50 is marginal. Far from offering double the blockage, SPF 100 blocks 99 percent of UVB rays, while SPF 50 blocks 98 percent. (SPF 30, that old-timer, holds its own, deflecting 96.7 percent).