"It may be tempting to make the reindeer food sparkle, but please don’t use glitter and sequins.. Anything made from plastic can cause stomach problems for most animals if eaten. Glitter is also a microplastic; the pieces are so small and so could cause a problem for the environment for a long time. Cake sprinkles or edible glitter should also be avoided as they tend to contain e-numbers."
www.rspb.org.uk/about-the-rspb/about-us/media-centre/press-releases/glittersnotgoldforwildlife/