As a general rule, piercings/tattoos are not good ideas because they can lead to infection. It's best to consult with a nurse in your physician's practice. The conditions would have to be most sterile for any piercings - or pedicures for that matter. If the blood sugars are in control, and your medical team knows of a place that has met some hygiene standard, then sit can be better to let the teenager have a piercing or a tattoo. Keep in mind that a teenager can do it on his/her own in far less safe places.