Only downside I can think of is that powder would absorb moisture from the air. Best case is you have something living in the kit. Almost-worst case would be if the blanket somehow delaminated as a result. Worst case on thier part would be if someone was allergic to the whatever.

Just a theory. I think there should be something in them to, and this is all I've been able to come up with after years of puzzling it out.