One can approach this problem by taking a closer look at a piercing’s effect on the skin. Once a piercing is made, a small hole and tunnel is created through the skin. The body tries to heal this injury by creating layers of skin cells to cover up the defect. The piercing would thus normally close over after a short time, however it remains open due to the presence of the metal piercing in place and the layers of skin cells actually line and seal the tunnel walls in effect healing the wound around the hole. Once a piercing is removed, there is no open injury that the body needs to heal and the hole can remain open and stable for quite some time. The outer skin layer replaces itself more or less every month and the old cells on the surface die and flake off. These are usually washed away, however inside this piercing tunnel these cells can become trapped and surrounded by bacteria. This causes the bad smell. Keep these old piercing holes clean with cleansers designed for sensitive skins and rinse them thoroughly. Never use alcohol-based cleansers on these areas. If the skin becomes dry, use a polyhydroxy-acid moisturizer. A short course of antiseptic cream can be used if there is any bad smell. Any piercing that is swelling or oozing or painful should be checked by your medical doctor for perhaps a deeper infection.