Tin oxide is a water-insoluble, inorganic metal compound used in cosmetic products primarily as an opacifier, viscosity regulator, and filler. Due to its opacifying properties, it lends formulations a more opaque appearance. It is used in low concentrations in both wash-off and leave-on products. (1) (2)

1 Bährle-Rapp, M. (2012). Springer Lexikon Kosmetik und Körperpflege. 4th revised and expanded edition. Springer.

2 Bergfeld, WF, & Liebler, DC (2014). Safety assessment of tin(IV) oxide as used in cosmetics. International Journal of Toxicology, 33(1_suppl), 40–46.