Electrodermal screening itself is relatively safe, although people with implanted pacemakers should avoid electrical current.  Let the practitioner know if you have a pacemaker.  

Electrodermal screening has its earliest roots in what was called galvanic skin testing. The galvanic skin response, a method of measuring the electrical resistance of the skin, was discovered in the early 1900s. Galvanic skin testing detects sweat on the skin, and more sweat produces better electrical conduction.

In the 1950s, a West German physician and acupuncturist named Reinhold Voll combined acupuncture theory with galvanic skin response technology. He tested the skin along various points with particular attention to the acupuncture meridians.  

Galvanic skin response changes are still used in lie detector tests, along with several other measures such as pulse, breathing, and blood pressure.

Electro-dermal screening is a galvanized skin response that measures the electrical resistance on the skin’s surface. The purpose is to detect energy imbalances along invisible lines of the body described by acupuncturists as meridians.

The testing device sends a tiny electrical current, too small to be detected by the patient, through a probe. The patient may hold a probe in one hand, while a second probe is touched to another part of the body. This completes a low-voltage electrical circuit, and a computer screen or a needle on a gauge reads out a number between 0 and 100. This may be repeated at many different places on the skin. These numbers are used to decide if the patient’s energy is out of balance.

If the patient is being tested for a type of treatment, samples of various remedies may be tried as the probe is touched to the problem area. Remedies may include homeopathic liquids and dietary or vitamin supplements. Different substances are tested until one is found that “balances” the energy disturbance.

Here is a description of electro-dermal screening and what it can be used for by Dr. William LaValley.