A source of electric current applied to any part of a patient's body determines an electrical field between the electrodes and through tissue. In this electrical field, the positive particles are attracted by the negative pole and the negative particles by the positive pole. In other words, migration of charged particles (electrophoresis) is produced in tissue that an electrical field crosses. This migration is significant if the electric current remains stable with sufficient intensity and for a long enough time.

Direct current, still also called galvanic current today, i.e. with constant intensity over time, is therefore used to mobilize charged particles through tissue. If these charged particles are medicinal, the direct current will act as a vector allowing introduction and penetration of medicinal substances.

This technique, which consists in introducing electrically-charged medicinal substances by applying direct current, is referred to as iontophoresis in international nomenclature.