A better option is diatomaceous earth. It's crushed seashells; you can buy it at any pool supply store and it's non-toxic and super fine. I have used it many times. I even put it on my dogs and on their bedding. It can even be used in fish tanks, it's all natural and non-toxic. I would check into that. As far as the egg shells, I'm not sure about that one. Hope that helps.