Is body art harmful if you don't do it right?

Yes: Any physical acitivity, any sport, any new use of muscles groups not used before for an activity can be harmful. If everyone did all their physical activity--including sitting, walking, eating, getting dressed, bending, picking up stuff on ground--correctly, america's bill would be a fraction what it is today.

Depends: Are you talking about tattoos or just applying body paint? Tattoos usually are safe but if the artist is not conscientious, you could get hepatitis or some other infectious illness. Really ethical tattoo artists will not do a face, palms, soles, genitals and will ask about your expectations and what your career choices might be since tattoos in the wrong place can limit job options.