Here's a way to add glitter to cakes without putting a non-food product/plastic particles/ IBS inducing item onto people's food. Just say no to plastic that you make people eat, and make sure that anything inedible is removable.
Tylose powder is available in my shop here: Tylose for Glitter Glaze
And here's the recipe for a stay-put glitter application for gumpaste:
2 Tbsp hot water
1/4 tsp tylose
disco dust or micro glitter
Put the water in a container and sprinkle the tylose on top. Mix with a fork and try to break up as much of the tylose as you can since it tends to clump up. Add the glitter (as much as you want) and stir it up, then let it sit until it all gels. Apply with a paintbrush and store at room temp in a sealed container. Paint it on the dried gumpaste, using multiple coats to build up the glittery surface, and drying between coats.
Kara Buntin owns A Cake To Remember LLC, online cake supplies at www.acaketoremember.com and www.acaketoremember.etsy.com