There is the risk of getting a very serious infection. If you get a simple infection the area where you got the piercing will get red and sore. The hole usually fills in and you have to get it repierced. But if you get a really bad infection then you sometimes have to get a tetanus shot and that's not fun. You can even get blood poisoning if the equipment isn't sterilized. Most piercings are safe, but naval piercings carry a greater risk of infection. The reason is because the skin around your belly stretches and bends and irritates the belly button piercing. Also, because this area is covered most of the time, there is less air circulation so the piercing heals slower. Some people are allergic to nickel which is a type of material used for the piercing. The best and safest way to avoid this is to use high quality jewelry. It can take up to six months for a belly button piercing to heal completely.