A zinc oxide powder is described, which, when used in a dispersion at a concentrationof at least 50 wt% of zinc oxide, produces a transparent composition having a totalvisible transmittance through a path length of 20 microns at 550nm of at leastone of； at least 70%, at least 75%, at least 80% or at least 85%. The powder has a numberaverage zinc oxide aggregate size of at least 0.8 microns, at least 1 micron, atleast 2 microns or at least 3 microns. Use of the zinc oxide powder reduces the riskof transdermal penetration.
