Editor's Picks

Titanium dioxide and zinc oxide sunscreens have generally been thought to protect by physically blocking and scattering UV radiation. Cole C. et al. measured transmission and reflectance and found that the average range of reflection for titanium dioxide and zinc oxide was only 4–5%, providing minimal protection via this mechanism (see article in this issue on page 5–10: Metal oxide sunscreens protect skin by absorption, not by reflection or scattering). Contrary to popular belief, these sunscreen filters work similar to organic ‘chemical’ soluble filters and absorb UV rays acting as semiconductors with clearly defined band gap energy. They reflect and scatter radiation only in the visible wavelengths at photon energy above this semiconductor band gap energy. This mechanism of protection does not alter the usefulness of these filters, but understanding it will help in the development of more efficient sunscreen products.