Erythrosine, also called Red Dye No. 3, is used as a colourant in various foods, including toffees, candies, and drinks. On the labels of these products, it may simply appear as "Number 3.

Erythrosine, which is more likely to show up as FD&C Red No. 3 or Red 3 on an ingredients label, is a color additive in food products, dietary supplements, and medicines like cough syrup.