What causes odor and leakage in the belly button?

Skin infection: A skin infection centered in the belly button can do that (especially if overweight or the area is not exposed to air). The first step is gentle cleaning with an antibacterial soap daily. There are rare conditions that can cause an opening of a congenital tract that leads to your belly button - either way, if this perssists, it makes sense to get this checked out by your doctor.