Glitter, Cosmetics + The FDA
So you'd like to know if you can use glitter in cosmetics? And you've SEEN glitter in cosmetics, so it must be ok, right? Well... welcome to the grey area of glitter and the FDA.
Here's the gist: the FDA regulates cosmetics (this excludes soap, of course) and what color additives can be used in their manufacture. Once they've reviewed an individual product, they either permit its use (and specify the type of use - eyes, lips, external) or they do not. Permitted colors and their permitted uses are posted on their site, here. If something isn't on a specific use's list of permitted additives, it's not technically allowed to be used as a colorant for that use.
Here's the grey part: although glitter is NOT on the approved list, the FDA has enacted a grace period during which time enforcement of the regulations will be discretionary. We have seen this discretionary enforcement information dating back as far as 2012, and there has been no mention of any changes to the grace period that we've been able to find.
In the end, all we can do is provide the information we've been able to obtain; it is up to end users to decide what they are comfortable with.
For use outside of the United States, please check the laws in your area.