Antioxidants in Polypodium leucotomos, a tropical fern, can technically block UV radiation. But antioxidants are unstable molecules, so getting them from stomach to skin is hard. Today’s fern-extract pills, like Solaricare or Heliocare, reach only SPF 4, not nearly enough for daily protection, let alone a beach day. This instability issue won’t be solved soon, so keep slathering up.
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This article was originally published in the January/February 2017 issue of Popular Science, under the title “I Wish Someone Would Invent…A Sunscreen Pill.”