For some reason I cannot comment on my post to respond to replies that I have gotten but I can make new post. I don't believe that they local bakery uses actual glitter in their frosting because yes that would be unsafe. I did find two pictures online of some of their work that has the glitter. It doesn't look as sparkly as I remember seeing it in person on a cake but that was a year or more ago.

I have never heard of disco dust until doing some research last night.

That looks like edible gum arabic cake sparkles, possibly ground finer by using tea strainer and a knife handle or a pepper mill, sprinkled on after the icing has been applied.  It hasn't been mixed into the icing--you'd never see any shine if that was done.

yes what she said ^^