Mascara contains the crystalline form of guanine, a word that derives from the Spanish word guano, meaning “dung.” Guanine is used extensively in the cosmetics industry, where it functions as a colorant and as an opacifying (shimmering or light diffusing) agent. read more
While mascara and various other cosmetics contain guanine, which is used to give a pearlescent look, this is not guano and does not come from guano. It is made from fish scales though. So, no bat feces; but crushed-up fish scales. read more