Basically, the present invention is directed to a new and improved system for the therapeutic use of currents which includes conducting direct electrical current through the skin of a body being treated, and periodically reversing the electrical current and conducting the current through the skin in the opposite direction, to effectively deliver very low frequency AC current, substantially in the critical range of approximately 0.0027 Hz to 20 Hz. It has been discovered that, within this substantially critical frequency window between approximately six minutes per full cycle and approximately ten cycles per second, a dramatic cancellation of skin damaging ions takes place. At frequencies higher than approximately 20 Hz, the effect is to diminish its DC-like blood stimulation. At frequencies lower than approximately 0.0027 Hz, the risk of skin injury increases substantially. It is well known that the positive electrode unfortunately produces skin damaging hydrochloric acid. Likewise, the negative electrode unfortunately also produces skin damaging sodium hydroxide. However, within the aforementioned frequency range of the present invention, either polarity stimulates blood circulation, but also cancels the undesired skin damaging ions with the reverse portion of the electrical cycle. The reason for neutralization of the harsh injury producing chemicals, i.e., hydrochloric acid and sodium hydroxide, is that both of these chemicals require a finite period of time on the skin to cause damage. Hence, these damaging chemicals are made to cancel each other before damage takes place, by critical frequency selection, in accordance with the invention, of the AC driving signal. Therefore, optimization of a long sought electrotherapeutic device with reduced side effects has been achieved. Another use of the safe AC currents cited above and/or a DC signal with charged membranes preventing injury is its application to wound healing. The conductive electrodes for these devices may take either of two forms, i.e., one may be non-metallic carbon-filled silicone or, preferably of powdered carbon particles. A second form may be a metallic electrode preferably of aluminum, copper, zinc and/or magnesium as examples of metallic electrodes but not necessarily limited to these metals. These metals are preferably in powdered form and contained within a porous membrane with a small opening to attach a conductive lead to a battery source. Still other applications of the innovative use in electrotherapy of charged membranes and/or powdered metal electrodes is its use for drug delivery and diagnostic purposes. For instance, a membrane enclosed stainless steel powdered negative electrode may be used in the pickup probe for glucose detection. Charged membranes would surround the probe as an intervenor between skin and the electrode.