What Causes Numbness In The Toes?

For a couple of months now, maybe longer, I have a numbness between my big toe and the toe next to it, it goes up across the top of my foot. I don't notice the numbness until i actually touch my foot and then it just feels like i had a shot of Novocaine in my foot that is wearing off some, not total numbness but not normal at all. What could be causing this?