6.  Allergies
Your pre-teen may not even be aware of the fact that he/she might have an allergy to certain metals, such as nickel, a realization that will (if they are indeed allergic) likely show itself within 6-24 hours of the piercing. Symptoms of nickel allergies include dark, leathery, cracked skin that becomes even more irritated with sweating. If you and your pre-teen are already aware of a nickel allergy, it’s a good idea to avoid piercing guns, as they may contain nickel and can cause bacterial infections.