You can try and Google it, other wise if not stated it’s probably not safe. Go to a craft store and get trusted India ink or something reliable if you can. They’re not too expesive, like $3-$5 per bottle.
As long as it specifically says non toxic and acid free you shouldn’t have any problems!
I would LOVE to see more of all your stick n pokes! I love seeing your art, so submit me more! -Hailey