A water-soluble absorber of ultraviolet B radiation, used topically as a sunscreen. It does protect skin from UVA rays as well, but not as well as it protects from UVB. For complete skin protection, this ingredient (as well as many other UVB-protecting sunscreen ingredients) must be paired with other UVA-protecting ingredients (including avobenzone, titanium dioxide, zinc oxide, or Mexoryl SX), according to Paula’s Choice.