Historically, indigo was a natural dye extracted from plants, and this process was important economically because blue dyes were once rare. Nearly all indigo dye produced today — several thousand tons each year — is synthetic.
In the U.S., the Food and Drug Administration (FDA) does not approve or review cosmetics, although it does regulate the colors that can be used in the hair dyes. The cosmetic companies are not required to report injuries resulting from use of their produc
