Tongue piercings may be trendy, but biting down on the metal stud can crack a tooth. Lip piercings pose a similar risk. And when metal rubs against the gums, it can cause gum damage that may lead to tooth loss. The mouth is also a haven for bacteria, so piercings raise the risk of infections and sores. Also, with a tongue piercing there is a risk of accidentally piercing a large blood vessel, which can cause severe bleeding. Bottom line, discuss the health risks with your dentist first.