Is She Old Enough for Deodorant?

It seems like kids, especially girls, are using adult beauty products at much younger ages. For example, nail polish. Forget it; it's not uncommon to see little girls as young as two with some on. But what about deodorant? I'm imagining that everyone in the house knows when it's the right time ;). But really, when is the right time? Is there such thing as too soon?