Scars: Areas where the epidermis of the skin has been cut
Traumas: Previous areas of trauma where either there are no visible scars or an abnormality (bruise or sore) does not heal in a reasonable amount of time
Piercings: Scars from earring piercings, body piercings, etc.
Metal inside the body: surgical pins, plates, mesh, bullet or shrapnel fragments, dental metals
Injections: dental anesthetics, neural therapy, IV drips, drugs or vitamins (such as B-12 shots)
Dental decay and other dental toxins:
Be sure to check out "The SPLAT Effect" and "Double Jeopardy".