Via press release from the FDA:
FDA wants you to be aware that some decorative glitters and dusts promoted for use on foods may, in fact, contain materials that should not be eaten.
Many decorative glitters and dusts are sold over the Internet and in craft and bakery supply stores under names such as luster dust, disco dust, twinkle dust, sparkle dust, highlighter, shimmer powder, pearl dust, and petal dust.
Moreover, a variety of online instructional videos, blogs, and articles promote the use of these glitters and dusts to decorate foods such as cakes, cupcakes, and cake pops.
There are some glitters and dusts that are edible and produced specifically for use on foods. These products are made from ingredients that may be safely eaten. But others may not.
More details are at the link.