Gold Worst Colouring Agent/Pigment No known benefits Gold description Common sensitizer that can induce negative responses on skin, especially on the face and eyelids. Claims of gold helping to create electric charges in skin to trigger improvement in signs of ageing are completely unproven. Another form of gold used in skincare products is “colloidal gold,” which means that the gold particles have been nanosized (usually to 1-15 nanometers) so that it remains dispersed evenly throughout a solution. Although gold is a heavy metal, and heavy metals are subject to regulations, colloidal gold preparations are not regulated, so the risks are unknown. Initial research shows that it is fairly safe. Colloidal gold also is used in the world of medicine, where there is a minor amount of research that it might have benefit because of assumed skin-soothing properties. Most of that research, however, is either very old or was performed on only a very small group of people, not enough to prove efficacy. Even if gold were a good skin-soothing agent, its effects have never been compared with the effects of the numerous potent and stable skin-soothing ingredients that are commonly used in skincare products and that have a great deal of research proving their benefit and safety. What is for certain: There is no published research proving that gold, normal or colloidal in size, has any anti-ageing benefits.