Piercing, like tattooing, is just one of today’s popular forms of ―body art and self-expression. Piercing may seem daring, cool and totally safe because some celebrities use piercing to flaunt their particular style or attitude. But piercing the tongue, lips, cheeks or uvula (the tiny tissue that hangs at the back of the throat) is not as safe as some would have you believe. That’s because the mouth’s moist environment—home to huge amounts of breeding bacteria—is an ideal place for infection.
An oral piercing can interfere with speech, chewing or swallowing. That may seem like a mere inconvenience until you consider that it may also cause:

• Excessive drooling (something you won’t see in hip fashion magazines!)
• Infection, pain and swelling
• Chipped or cracked teeth
• Injuries to the gums
• Damage to fillings
• Increased saliva flow
• Hypersensitivity to metals
• Scar tissue
• Nerve damage

These harmful effects can happen during the piercing, soon after, or even long after the procedure.

An infection can quickly become life threatening if it’s not treated promptly. For example, oral piercing carries a potential risk of endocarditis, an inflammation of the heart valves or tissues. Bacteria can enter the bloodstream through the piercing site in the mouth and travel to the heart, where it can colonize on heart abnormalities. This is a risk for people with heart conditions and, in the worst of cases, results in death.

After a piercing the tongue may swell. There have been reports of swelling serious enough to block the airway. And it’s very possible to puncture a nerve during a tongue piercing. If this happens, you may experience a ―numb tongue—nerve damage that is sometimes temporary, but can be permanent. The injured nerve may affect your sense of taste, or how you move your mouth. And damage to the tongue’s blood vessels can cause serious blood loss.

In addition, piercing jewelry can sometimes cause allergic responses to the pierced site. The jewelry can even get in the way of dental care by blocking x-rays.
Don’t pierce on a whim. The piercing will be an added responsibility to your life, requiring constant attention and upkeep. Talk to your dentist for more information.

Source: ADA