As far as skincare is concerned, gold is said to minimize collagen depletion and boost elasticity. It helps to even out skin tone and brighten the skin. Gold nanoparticles used in the preparation are ~200 nm in size, largely spherical or facetted. They are synthesized under controlled conditions from H2AuCl4 in water using trace amounts of citric and tannic acids as reducing agent. There is a vast literature on the toxicology of gold nanoparticles because these materials are of use in drug delivery and medical imaging.