I was at a cake show recently and one of the vendors mentioned that most petal dusts are considered non-toxic but are not really to be consumed. Same for pearl and metallic dusts. I was just watching Joshua John Russell's Modern Piping course on Craftsy and he said to only use metallics sparingly as they do contain metals and could poison someone. He said that they should not be used to cover a whole cake.
I see lots of cakes on here that have entire tiers pearlized, lots of gold and silver on cakes, etc. I'm wondering, do you warn people?
I have only used dust sparingly in the past for accents, but I'm a little freaked out now and don't want to use them at all! I was planning on making some pearl-accented cookies, but now I'm thinking twice about it!